TY  - RPRT
TI  - What is Zelen's design?
AU  - D J Torgerson
AU  - M Roland
PY  - 1998
DO  - 10.1136/bmj.316.7131.606
UR  - https://pubmed.ncbi.nlm.nih.gov/9518917/
ID  - 9518917
ER  -