Yamamoto Kenkichi (山本 健吉, 1907-1988) was the pen-name of Ishibashi Teikichi, a Japanese writer and literary critic.
as "...the mid to late twentieth century's greatest scholar of Japanese haiku and related literature.
(Unlike many such books, Prof. Yamamoto's guides always indicate the parts of the seasons, an important feature for renku poets.)
Among other projects, Prof. Yamamoto served in this capacity for the ground-breaking six-volume Eigo Saijiki / An English & American Literary Calendar (1968-70), which examined our literature through the lens of the Japanese season word system.
"[4] This selective list, "The five hundred essential Japanese season words", translated by William J. Higginson and Kris Young Kondo (also edited by Higginson, is considered a standard by western haiku researchers and poets.