TY  - RPRT
TI  - Proper retrospective study.
AU  - G J Berdy
AU  - C W Roberts
PY  - 1989
DO  - 10.1016/s0886-3350(89)80124-5
UR  - https://pubmed.ncbi.nlm.nih.gov/2810101/
ID  - 2810101
ER  -