1. Fuzzy groups redefined;Anthony;J. Math. Anal. Appl.,1979
2. Closure systems and L-subalgebras;Biacino;Inform. Sci.,1984
3. Lattice Theory;Birkhoff,1967
4. S.-C. Cheng and Z.-D. Wang, Divisible TL-subroups and pure TL-subgroups, submiteed to Fuzzy Sets and Systems.
5. Fuzzy ideals and fuzzy prime ideals of a ring;Dixit;Fuzzy Sets and Systems,1991