By Tosio Kato
In view of contemporary improvement in perturbation conception, supplementary notes and a supplementary bibliography are further on the finish of the hot version. Little swap has been made within the textual content other than that the para graphs V-§ 4.5, VI-§ 4.3, and VIII-§ 1.4 were thoroughly rewritten, and a few minor error, quite often typographical, were corrected. the writer want to thank many readers who introduced the blunders to his cognizance. as a result of those alterations, a few theorems, lemmas, and formulation of the 1st variation are lacking from the hot variation whereas new ones are additional. the recent ones have numbers varied from these connected to the previous ones which they could have changed. regardless of substantial growth, the bibliography i" no longer meant to be whole. Berkeley, April 1976 TosIO RATO Preface to the 1st variation This booklet is meant to offer a scientific presentation of perturba tion concept for linear operators. it's was hoping that the booklet should be valuable to scholars in addition to to mature scientists, either in arithmetic and within the actual sciences.