Memo

Tables of symplectic actions on the K3 lattice (pdf)

In older versions (up to [v4, 29 Sep 2011]), #13, #19, #25, #37 and #62 are incorrect.

Lattices of type T (pdf)

I mean by "type T" a root lattice whose Dynkin diagram has three branches.

Resolution of a cusp singularity (pdf)

A singular point of a Hilbert modular surface defined by Q(\sqrt{5})