M. Akram, N. Gani and A. Borumand Saeid, Vague hypergraphs, Journal of Intelligent and Fuzzy Systems, 26, 647–653 (2014).
 M. Akram, F. Feng, S. Sarwar and Y.B. Jun, Certain types of vague graphs, University Politehnica of Bucharest Scientific Bulletin Series A, 76 (1), 141–154 (2014).
 R. A. Borzooei and H. Rashmanlou, Ring sum in product intuitionistic fuzzy graphs, Journal of advanced research in pure mathematics, 7 (1), 16–31 (2015).
 R. A. Borzooei and H. Rashmanlou, Domination in vague graphs and its applications, Journal of Intelligent and Fuzzy Systems, to appear.
 R. A. Borzooei and H. Rashmanlou, Degree of vertices in vague graphs, Journal of applied mathematics and informatics, to appear.
 W.-L. Gau and D. J. Buehrer, Vague sets, IEEE Transactions on Systems, Man and Cybernetics, 23 (2), 610–614 (1993).
 A. Kaufman, Introduction a la Theorie des Sous-Emsembles Flous, Vol. 1, Masson et Cie, 1973.
 J. N. Mordeson and P. S. Nair, Fuzzy Graphs and Fuzzy Hypergraphs, Physica, Heidelberg, Germany, 2nd edition, 2001.
 M. Pal and H. Rashmanlou, Irregular interval- valued fuzzy graphs, Annals of Pure and Applied Mathematics, 3 (1),
 N. Ramakrishna,Vague graphs, International Journal of Computational Cognition, 7, 51–58 (2009).
 H. Rashmanlou and M. Pal, Antipodal interval-valued fuzzy graphs, International Journal of Applications of Fuzzy Sets and Artificial Intelligence, 3, 107–130 (2013).
 H. Rashmanlou and M. Pal, Balanced interval-valued fuzzy graph, Journal of Physical Sciences, 17, 43–57 (2013).
 H. Rashmanlou and M. Pal, Some properties of highly irregular interval-valued fuzzy graphs, World Applied Sciences Journal, 27 (12), 1756–1773 (2013).
 H. Rashmanlou, S. Samanta, M. Pal and R. A. Borzooei, A study on bipolar fuzzy graphs, Journal of Intelligent and Fuzzy Systems, 28, 571–580 (2015).
 H. Rashmanlou and Y. B. Jun, Complete interval-valued fuzzy graphs, Annals of Fuzzy Mathematics and Informatics, 6 (3), 677–687 (2013).
 A. Rosenfeld, Fuzzy graphs, Fuzzy Sets and their Applications (L. A. Zadeh, K. S. Fu, and M. Shimura, Eds.), Academic Press, New York, 77–95, 1975.
 S. Samanta and M. Pal, Fuzzy tolerance graphs, International Journal Latest Trend Math, 1 (2), 57–67 (2011).
 S. Samanta and M. Pal, Fuzzy threshold graphs, CiiT International Journal of Fuzzy Systems, 3 (12), 360–364 (2011).
 A. A. Talebi, H. Rashmanlou, N. Mehdipoor, Isomorphism on vague graphs, Annals of Fuzzy Mathematics and Informatics, 6 (3), 575–588 (2013).
 A. A. Talebi, N. Mehdipoor, H. Rashmanlou, Some operations on vague graphs, Journal of Advanced Research in Pure Mathematics, 6 (1), 61–77 (2014).
 L. A. Zadeh, Fuzzy sets, Information and Control 8, 338–353 (1965).
 L. A. Zadeh, Similarity relations and fuzzy ordering, Information Sciences, 3, 177–200 (1971).
 L. A. Zadeh, Is there a need for fuzzy logical, Information Sciences, 178 , 2751–2779 (2008).