OpenStax textbook
Links to the appropriate OpenStax book sections are listed in the Bruce’s notes for the topic.
Links to the appropriate sections are also listed with the homework problems for the topic.
For buffer solutions, read OpenStax Section 14.6 Buffers
Other reading
For Common Ion effect, read this link from LibreTexts to better understand the common ion effect, paying special attention to the section “Common ion effect with weak acids and bases”