The method of therapeutically useful, / 3 S (Z) / - 2 - /// 1- (2-amino-4-thiazolyl) -2 - // 2,2-dimethyl-4-oxo-1- (sulfooxy) - 3-azetidinyl / amino / -2-oxoethylidene / amino / oxy / acetic acid and the preparation of crystalline dierytromysiini- dikoliinisuolojen