1. Characterization of β-lactamase deficient (bla) mutants of the R-plasmid R 1 in Escherichia coli K-12 and comparison with similar mutants of RP 1;Crowlesmith;Antimicrob. Agents Chemother,1980
2. Correlation of β-lactamase production and resistance to β-lactam antibiotics in Enterobacteriaceae;Cullman;Zbl. Bakt. Hyg., I. Abt. Orig. A,1982
3. Antibiotic sensitivity testing. Report of an international collaborative study;Ericson;Acta path, microbiol. scand. Sect. B.,1971
4. Bakteriologische Grundlagen der chemotherapeutischen Laboratoriumspraxis;Klein,1957
5. Types of β-lactamase determined by plasmids in gram-negative bacteria;Matthew;J. Bact,1979