TY  - RPRT
TI  - Planning a longitudinal study. I. Sample size determination.
AU  - J J Schlesselman
PY  - 1973
DO  - 10.1016/0021-9681(73)90060-x
UR  - https://pubmed.ncbi.nlm.nih.gov/4759580/
ID  - 4759580
ER  -