“…Many other authors contributed to the study of fractional powers of generators through the above integral algorithms or alternative algorithms using powers of the resolvent of H, and summaries of the subject from various aspects, at various stages of its development, with extensive references and applications, can be found in the books of Yosida [22], Friedman [9], Krasnoselskii et al [13], Triebel [20], Tanabe [19], and Pazy [16]. A comprehensive description of the subject is also given in the series of papers by Komatsu [11].…”