https://arxiv.org/abs/hep-th/0010091
[hep-th/0010091] Discrete Wilson Lines in N=1 D=4 Type IIB Orientifolds: A Systematic Exploration...
Abstract page for arXiv paper hep-th/0010091: Discrete Wilson Lines in N=1 D=4 Type IIB Orientifolds: A Systematic Exploration for $\IZ_6$ Orientifold