4-Thia-1-azabicyclo(3.2.0)heptane-2-carboxylic acid, 3,3-dimethyl-6-(((5-methyl-3-phenyl-4-isoxazolyl)carbonyl)amino)-7-oxo-, (2S-(2alpha,5alpha,6beta))-, mixt. with (2S-(2alpha,5alpha,6beta(S*)))-3,3-dimethyl-6-(((((3-(methylsulfonyl)-2-oxo-1-imidazolidinyl)carbonyl)amino)phenylacetyl)amino)-7-oxo-4-thia-1-azabicyclo(3.2.0)heptane-2-carboxylic acid