《汉语拼音方案》规定:声调符号要标在主要元音(即韵腹)上。但中等师范学校教材《语文基础知识》语音部分,在讲到声调时说:“汉语六个主要元音中,发音最响亮的是a,依次下去是o,e,i,u,ü。一个音节有a,调号就标在a上;没有a就标在o或e上,碰到iu、ui组成的音节,就标在最后一个元音上。调号如标在i上,i上的一点就可以省去。”教材还提到一首帮助掌握标调方 The Chinese Phonetic Alphabet Scheme stipulates that the tone symbol should be marked on the main vowel (ie, the rhyme). However, in the phonetic part of the “Basic Knowledge of Chinese Language” textbook in secondary normal schools, when speaking about tone, “The six most important vowels in Chinese are pronounced a with the loudest sound, and in turn they are o, e, i, u, ü. The syllables have a, and the key numbers are marked on a; if there is no a, they are marked on o or e, and the syllables composed of iu and ui are marked on the last vowel. The key number is marked on i, i. The one point can be saved." The textbook also mentioned a help to master the calibration