Reference 1
https://www.ejmste.com/article/chess-training-and-mathematical-problem-solving-the-role-of-teaching-heuristics-in-transfer-of-4483
This study shows that chess instruction that explicitly teaches heuristics led to better performance in mathematical problem solving.

Reference 2
https://www.chess.com/blog/OnlineChessTeacher/the-role-of-chess-in-education-building-critical-thinking-and-problem-solving-skills?utm
Discusses how chess fosters critical thinking, logical reasoning, planning and transversal skills.

Reference 3
Trinchero, R., & Sala, G. (2016). Chess training and mathematical problem‑solving: the role of teaching heuristics in transfer of learning. Eurasia Journal of Mathematics, Science & Technology Education, 12(3), 655‑668.

Reference 4
Sala, G., & Gobet, F. (2017). Does chess instruction improve mathematical problem‑solving ability? Two experimental studies with an active control group. Learning & Behavior, 45, 414‑421

Reference 5
https://www.nature.com/research-intelligence/nri-topic-summaries/cognitive-skills-and-development-in-chess-players-micro-286883?utm
Discusses how chess training may relate to attention, memory, fluid reasoning, and transfer issues.

Reference 6
https://chessineducation.org/the-politics-of-chess-in-education-part-1/?utm
Focuses on issues around teaching transversal (or “21st century”) skills via chess programs.