If you are looking for developments in Isabelle/HOL, there is the AFP: https://www.isa-afp.org/
There is also a recent book that might interest you: http://www.concrete-semantics.org/
If you are looking for developments in Isabelle/HOL, there is the AFP: https://www.isa-afp.org/
There is also a recent book that might interest you: http://www.concrete-semantics.org/