(Q24558950)
Statements
Observational versus experimental studies: what's the evidence for a hierarchy? (English)
0 references
July 2004
0 references
1
0 references
3
0 references
341-7
0 references
2 references
1 reference
1 reference
1 reference
1 reference
1 reference
1 reference
1 reference
1 reference
1 reference
1 reference
1 reference
1 reference
1 reference
1 reference