TY  - GEN
AU  - Kramer,M S
AU  - Boivin,J F
TI  - Directionality, timing, and sample selection in epidemiologic research design
SN  - 0895-4356
PY  - 1989///1026
KW  - Epidemiologic Methods
KW  - Research Design
KW  - Sampling Studies
N1  - Publication Type: Journal Article
UR  - https://doi.org/10.1016/0895-4356(89)90094-2
ER  -