For those who're not familiar with PLT Redex Team and wanna take a look at Redex.

• Redex Doc(short tutorial + long tutorial)
• An Introduction to Redex with Abstracting Abstract Machines by David Van Horn
• Experimenting with Languages in Redex by William J. Bowman

• Automated Testing for Operational Semantics from Burke Fetscher

• OPLSS Talks by David Van Horn

• Semantics Engineering with PLT Redex

• CPSC 539B – Compiler Theory by William J. Bowman
• CMSC631 Program Analysis and Understanding by David Van Horn

• racket/redex repo

• PLT Redex FAQ

Evaluation context has been hevaily used in PLT Redex examples. Some links below may help :)

• Why do I need evaluation contexts in Redex?
• Evaluation context in textbook PFPL