[1] S. Banach, Theorie des Operations Lineaires, Monografje Matematyczne, TOM I, 1932.
[2] P. Corsini, Prolegomena of Hypergroup Theory, Second Edition, Aviani editor, 1993.
[3] P. Corsini, Hypergraphs and hypergroups, Algebra Univer. 35 (1996), 548–555.
[4] P. Corsini and V. Leoreanu, Applications of Hyperstructures Theory, Advanced in Mathematics, Kluwer Academic Publisher, 2003.
[5] B. Davvaz and T. Vougiouklis, A Walk Through Weak Hyperstructures: Hv-Structure, World Scientific Publishing Co. Pte. Ltd., Hackensack, NJ, 2019.
[6] I. Gelfand, Normierte ringe, Mat. Sbornik 9 (1941), no. 1, 3–24.
[7] K. Hamidizadeh, S. Mirvakili, R. Manaviyat, and H. Naraghi, A comparative analysis of hypergroupoids derived from metric spaces, Int. J. Nonlinear Anal. to appear.
[8] F. Hausdorff, Grundzuge der Mengenlehre, Vol. 7, von Veit, 1914.
[9] A. Nikkhah, B. Davvaz, and S. Mirvakili, Hypergroups constructed from hypergraphs, Filomat 32 (2018), no. 10, 3487–3494.
[10] W. Rudin, Principles of Mathematical Analysis, McGraw-Hill, New York, 1976.
[11] J. Von Neumann, Einige satze ubermessbare abbildungen, Ann. Math. 33 (1932), no. 3, 574–586.