where is common directory？

[ydsungan]

#include "common/permutation.hpp"
#include "common/sorting.hpp"
#include "common/timer.hpp"

where are these .hpp files?

[whatsthecraic]

It was a git submodule pointing to https://github.com/whatsthecraic/libcommon. But as the project is now completed, I've just integrated it into the main source code, together with merging the branch feature/vectorization, which contains the changes described in the Errata.