Gwoyeu Romatzyh
"Hanyu Pinyin" was based on several existing systems: "Gwoyeu Romatzyh" of 1928, "Latinxua Sin Wenz" of 1931, and the diacritic markings from "zhuyin" (bopomofo). "I'm not the father of pinyin," Zhou said years later; "I'm the son of pinyin. It's [the result of] a long tradition from the later years of the Qing dynasty down to today. But we restudied the problem and revisited it and made it more perfect."