p. 599 - 603
(2007/10/02)(2R,6R,7R)-7-Benzoylamino-3-methylene-8-oxo-5-oxa-1-aza-bicyclo[4.2.0]octane-2-carboxylic acid benzhydryl ester
(2S,6R,7R)-7-Benzoylamino-3-chloro-3-hydroxymethyl-8-oxo-5-oxa-1-aza-bicyclo[4.2.0]octane-2-carboxylic acid benzhydryl ester