TY  - RPRT
TI  - Sampling: the source of the data.
AU  - J A Heermann
AU  - M E Megel
PY  - 1994
DO  - 10.1097/00006527-199403000-00014
UR  - https://pubmed.ncbi.nlm.nih.gov/7800765/
ID  - 7800765
ER  -