A list of references can be found in the references section. Here we simply point to some of them of which may be of interest to the reader.
The original FCIQMC method is in Ref [2].
Quite a bit of symmetries and some details on the initiator method that is actually implemented is in Ref [12].
Linear scaling algorithm, (uniform) excitation generation and overall algorithm of FCIQMC is in Ref [13].
Density matrices, real walker weights and sampling bias is in Ref [14].
The KP-FCIQMC method is in Ref [8].
Error (blocking) analysis is described in Ref [4].