for PETSc v3.16.5

C codes (Chapters 1--12) were tested with PETSc 3.16.5 (main branch, commit 383c7071)

Python codes (Chapters 13--14) were tested with Firedrake commit e5c4aa61

Gmsh version 4.9.3 (and 4.9.0)

Test machine: bueler-thelio ubuntu 20.04