Yabla Pinyin Chart
https://chinese.yabla.com/chinese-pinyin-chart.php
Tips for Chinese Pronunciation from New Concept Chinese
https://www.newconceptmandarin.com/chinese-pronunciation/
Tingyiting (听一听)
Mandarin Pronunciation
https://routledgetextbooks.com/textbooks/9781138101111/lesson1.php
Pinyin Practice and Self-Quiz–Challenge Yourself