1. Introduction to Percolation Theory;Stauffer,1994
2. Fractals and Disordered Systems;Bunde,1996
3. Percolation Structures and Processes;Kinzel,1983
4. A comprehensive recent overview over directed percolation is given in H. Hinrichsen, Adv. Phys. 49 (2001) 815
5. Percolation processes