Mathematical Thinking and Learning is one of the major journals within mathematics education research, and the fourth issue of the journal has now been published. This issue contains the following three articles:

• Advanced mathematical knowledge in teaching practice: perceptions of secondary mathematics teachers, by Rina Zazkis and Roza Leikin.
• Understanding the development of flexibility in struggling algebra students, by Kristie Jones Newton, Jon R. Star and Kathleen Lynch.
• Mathematics majors’ perceptions of conviction, validity, and proof, by Keith Weber.

To learn more about these articles, visit the links above to read their abstracts!