TY  - RPRT
TI  - Directed selective pressure on a beta-lactamase to analyse molecular changes involved in development of enzyme function.
AU  - A Hall
AU  - J R Knowles
DO  - 10.1038/264803a0
UR  - https://pubmed.ncbi.nlm.nih.gov/796732/
ID  - 796732
ER  -