Man pages matching name xmcvtxmstringtoct in section 3:

XmCvtXmStringToCT.3.en	debian 10 / libmotif-dev
XmCvtXmStringToCT.3.en	debian 11 / libmotif-dev
XmCvtXmStringToCT.3.en	debian 12 / libmotif-dev