411 REFERENCE · Wikibooks
Pinyin/Four-corner System
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Pinyin#Pinyin tone marking
Sihjiaao Haohmaa
411 REFERENCE · Wikibooks
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.