(Q36410416)

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

3 March 2020

title

Genetic factors moderate everyday physical activity effects on executive functions in aging: Evidence from the Victoria Longitudinal Study (English)

1 reference

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

3 March 2020

1

1 reference

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

3 March 2020

Sandra Wiebe

3

1 reference

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

3 March 2020

Kaarin J. Anstey

4

1 reference

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

3 March 2020

author name string

G Peggy McFall

2

1 reference

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

3 March 2020

Roger A Dixon

5

1 reference

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

3 March 2020

publication date

1 January 2016

1 reference

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

3 March 2020

1 reference

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

3 March 2020

volume

30

1 reference

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

3 March 2020

issue

1

1 reference

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

3 March 2020

page(s)

6-17

1 reference

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

Synergistic associations of catechol-O-methyltransferase and brain-derived neurotrophic factor with executive function in aging are selective and modified by apolipoprotein E.

3 March 2020

cites work

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Neuroprotective effects of physical activity on the brain: a closer look at trophic factor signaling

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Physical activity and brain function in older adults at increased risk for Alzheimer's disease

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The impact of exercise on the cognitive functioning of healthy older adults: a systematic review and meta-analysis

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

IDE (rs6583817) polymorphism and pulse pressure are independently and interactively associated with level and change in executive function in older adults

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Lifestyle engagement affects cognitive status differences and trajectories on executive functions in older adults

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Brain-derived neurotrophic factor Val66Met polymorphism and cognitive function in persons with cardiovascular disease

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Taking up physical activity in later life and healthy ageing: the English longitudinal study of ageing

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Bridging animal and human models of exercise-induced brain plasticity

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The brain-derived neurotrophic factor Val66Met polymorphism moderates an effect of physical activity on working memory performance.

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

IDE (rs6583817) polymorphism and type 2 diabetes differentially modify executive function in older adults

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Genetic effects on old-age cognitive functioning: a population-based study

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Neurobiological markers of exercise-related brain plasticity in older adults

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Dynamic associations of change in physical activity and change in cognitive function: coordinated analyses of four longitudinal studies

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Late life leisure activities and risk of cognitive decline

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Mechanisms of brain aging regulation by insulin: implications for neurodegeneration in late-onset Alzheimer's disease

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Impact of the BDNF Val66Met polymorphism on cognition: implications for behavioral genetics

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Lifestyle and genetic contributions to cognitive decline and hippocampal structure and function in healthy aging

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The association between aerobic fitness and executive function is mediated by prefrontal cortex volume

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Do changes in lifestyle engagement moderate cognitive decline in normal aging? Evidence from the Victoria Longitudinal Study

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

BDNF Val66Met and cognition: all, none, or some? A meta-analysis of the genetic association

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Analyzing longitudinal data with missing values

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The aging hippocampus: interactions between exercise, depression, and BDNF

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Exercise, brain, and cognition across the life span

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Exercise training increases size of hippocampus and improves memory

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Physical activity predicts gray matter volume in late adulthood: the Cardiovascular Health Study

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Genetic variations in the CLU and PICALM genes are associated with cognitive function in the oldest old.

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Concordant association of insulin degrading enzyme gene (IDE) variants with IDE mRNA, Abeta, and Alzheimer's disease

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Changing perspectives regarding late-life dementia.

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Characterizing executive functioning in older special populations: from cognitively elite to cognitively impaired

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The impact of genetic research on our understanding of normal cognitive ageing: 1995 to 2009

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Effects of age, genes, and pulse pressure on executive functions in healthy adults

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Genetic contributions to age-related decline in executive function: a 10-year longitudinal study of COMT and BDNF polymorphisms

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Human aging magnifies genetic effects on executive functioning and working memory

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Impact of genetic variant BDNF (Val66Met) on brain structure and function

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Exercise builds brain health: key roles of growth factor cascades and inflammation

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

How Many Imputations are Really Needed? Some Practical Clarifications of Multiple Imputation Theory

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Differential aging of the brain: patterns, cognitive correlates and modifiers

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Insulin-like growth factor I interfaces with brain-derived neurotrophic factor-mediated synaptic plasticity to modulate aspects of exercise-induced cognitive function

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The relationship between impaired glucose tolerance, type 2 diabetes, and cognitive function

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Cognitive reserve and the neurobiology of cognitive aging

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The BDNF val66met polymorphism affects activity-dependent secretion of BDNF and human memory and hippocampal function

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Neurotrophins as synaptic modulators

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The unity and diversity of executive functions and their contributions to complex "Frontal Lobe" tasks: a latent variable analysis

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Isolation of specific interference processing in the Stroop task: PET activation studies

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

An application of prefrontal cortex function theory to cognitive aging

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

30 September 2017

Insulin-degrading enzyme

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Evidence for genetic mediation of executive control: a study of aging male twins

30 September 2017

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Physical activity, exercise, and physical fitness: definitions and distinctions for health-related research

28 June 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Cognitive ability, intraindividual variability, and common genetic variants of catechol-O-methyltransferase and brain-derived neurotrophic factor: a longitudinal study in a population-based sample of older adults.

28 June 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The benefits of staying active in old age: physical activity counteracts the negative influence of PICALM, BIN1, and CLU risk alleles on episodic memory functioning

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Preserved differentiation between physical activity and cognitive performance across young, middle, and older adulthood over 8 years.

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Effect of the BDNF Val66Met polymorphism on regional gray matter volumes and cognitive function in the Chinese population

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Acute aerobic exercise increases brain-derived neurotrophic factor levels in elderly with Alzheimer's disease.

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The Met-genotype of the BDNF Val66Met polymorphism is associated with reduced Stroop interference in elderly

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Effect of BDNF Val66Met polymorphism on normal variability of executive functions

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The genetics of cognitive ability and cognitive ageing in healthy older people.

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The Met-allele of the BDNF Val66Met polymorphism enhances task switching in elderly.

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Evidence for a release of brain-derived neurotrophic factor from the brain during exercise

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Physical activity and the maintenance of cognition: learning from animal models

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Brain-derived neurotrophic factor polymorphism Val66Met influences cognitive abilities in the elderly.

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The effect of acute exercise on serum brain-derived neurotrophic factor levels and cognitive function

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Serum neurotrophins--a study on the time course and influencing factors in a large old age sample

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Structure of four executive functioning tests in healthy older adults.

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The brain-derived neurotrophic factor Val66Met polymorphism is associated with age-related change in reasoning skills

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Leisure-time physical activity at midlife and the risk of dementia and Alzheimer's disease

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Brain-derived neurotrophic factor, phosphorylated cyclic AMP response element binding protein and neuropeptide Y decline as early as middle age in the dentate gyrus and CA1 and CA3 subfields of the hippocampus.

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

The impact of age, weight and gender on BDNF levels in human platelets and plasma

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Circulating insulin-like growth factor I mediates effects of exercise on the brain.

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Use it or lose it: engaged lifestyle as a buffer of cognitive decline in aging?

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Physical activity increases mRNA for brain-derived neurotrophic factor and nerve growth factor in rat brain

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Brain structure and function related to cognitive reserve variables in normal aging, mild cognitive impairment and Alzheimer's disease

21 September 2018

1 reference

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pmc&linkname=pmc_refs_pubmed&retmode=json&id=4693634

Performance on the Hayling and Brixton tests in older adults: norms and correlates

5 December 2018

1 reference

PubMed

https://pubmed.ncbi.nlm.nih.gov/26710092

inferred from PubMed ID database lookup

12 December 2020

based on heuristic

Identifiers

DOI

10.1037/NEU0000217

1 reference

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

3 March 2020

1 reference

https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:26710092%20AND%20SRC:MED&resulttype=core&format=json

3 March 2020

PubMed publication ID

26710092

1 reference