1) SAWAI, T.; K. MATSUBA & S. YAMAGISHI: A method for measuring the outer membrane-permeability of β-lactam antibiotics in Gram-negative bacteria. J. Antibiotics 30: 1134-1136, 1977
2) ZIMMERMANN, W. &, A. ROSSELET: Function of the outer membrane of <i>Escherichia coli</i> as a permeability barrier to beta-lactam antibiotics. Antimicr. Agents & Chemoth. 12: 368-372, 1977
3) FUJII-KURIYAMA, Y.; M. YAMAMOTO & S. SUGAWARA: Purification and properties of beta-lactamase from <i>Proteus morganii</i>. J. Bacteriol. 131: 726-734, 1977
4) SAWAI, T.; S. MITSUHASHI & S. YAMAGISHI: Stability of various derivatives of 7-aminocephalosporanic acid and 6-aminopenicillanic acid to cephalosporinases from Gram-negative bacteria. Proc. 6th Internat. Congr. Chemoth. I: 410-415, 1970