1. Continuous selections of linear functions and nonsmooth critical point theory;Bartels;Nonlinear Anal.,1995
2. Principles of Combinatorics;Berge,1971
3. Algebraic Graph Theory;Biggs,1996
4. Lattice-ordered rings;Birkhoff;An. Acad. Brasil Ciênc.,1956
5. Lattice Theory;Birkhoff,1979