1. G.J. Chang and G.L. Nemhauser, The k-domination and k-stability problems on sun-free chordal graphs, SIAM J. Algebraic Discrete Meth. 5 (1984) 332–345.
2. G.J. Chang, Centers of chordal graphs, Graphs and Combinatorics 7 (1991) 305–313.
3. V.D. Chepoi, Some properties of d-convexity in triangulated graphs (in Russian), Mathematical Researches (Chişinau) 87 (1986) 164–177.
4. V.D. Chepoi, Centers of triangulated graphs (in Russian), Matematiceskie Zametki (English Transl.: Mathematical Notes) 43 (1988) 143–151.
5. F.F. Dragan, Centers of graphs and Helly property (in Russian), PhD Thesis, Moldova State University, 1989.