 When a friend asked Zi Chan to explain ghosts, he gave what Yu calls "the locus classicus on the subject of the human soul in the Chinese tradition" ( Yu 1972 :372).
<clarity>  When a friend asked Zi Chan to explain ghosts, he gave what Yu calls "the locus classicus on the subject of the human soul in the Chinese tradition" ( Yu 1972 :372).
 When a friend asked Zi Chan to explain ghosts, he gave what Yu calls "the locus classicus on the subject of the human soul in the Chinese tradition" ( Yu 1972 , p. 372.