Complex sentence: The earliest known manual written about dominoes is the "(Manual of the Xuanhe Period)" written by Qu You (1341--1437), but some Chinese scholars believe this manual is a forgery from a later time.
Split into simpler sentences: The earliest known manual written about dominoes is the "(Manual of the Xuanhe Period)" written by Qu You (1341--1437). But some Chinese scholars believe this manual is a forgery from a later time.