TY  - RPRT
TI  - Problems in maintaining immunity to smallpox.
AU  - A S BENENSON
AU  - C H KEMPE
AU  - R E WHEELER
PY  - 1952
DO  - 10.2105/ajph.42.5_pt_1.535
UR  - https://pubmed.ncbi.nlm.nih.gov/14923964/
ID  - 14923964
ER  -