【乌焉成马】〖w yn chéng m〗[When a book is copied thrice, some characters become alike; printer's error; printing mistakes owing to similar forms]

乌多一撇蛇足添，

焉正与驴怎沾边。

成性豺狼剥削改，

马乌形似讹写舛。

指文字因形体相似而传写错误。Refers wrong transmission of writing due similar shape.