TY  - RPRT
TI  - Research problems and variables.
AU  - R J Harmon
AU  - G A Morgan
PY  - 1999
DO  - 10.1097/00004583-199906000-00029
UR  - https://pubmed.ncbi.nlm.nih.gov/10361800/
ID  - 10361800
ER  -