This is shown in Pinyin as follows: Note that the y, w, and yu replacements above do not change the pronunciation of the final in the final-only syllable.
For example, the variant sounds 挼 (ruá; ㄖㄨㄚˊ), 扽 (dèn; ㄉㄣˋ), 忒 (tēi; ㄊㄟ) are not used in guoyu.
Likewise the variant sound 孿 (lüán; ㄌㄩㄢˊ) is not recognized in putonghua, or it is folded into (luán; ㄌㄨㄢˊ).
For instance, 覅 (fiào; ㄈㄧㄠˋ) is a borrowing from Shanghainese (and other dialects of Wu Chinese) that are commonly used, and are thus included in most large dictionaries, even though it is usually labeled as a nonstandard regionalism (方, short for 方言 (topolect)), with the local reading viau [vjɔ], which is approximated in Standard Chinese as fiào.
Syllables in italics are considered nonstandard, and only exist in the form of regionalisms, neologisms or slang.