[1] I. Beg, M. Iqbal, Extension of linear 2-operators, Mathematica Montesnigri 2 (1993), 1-10.
[2] S. Cobzas, C. Mustata, Extension of bilinear functionals and best approximation in 2-normed spaces (to appear).
[3] N. Dunford, J.T. Schwartz, Linear Operators Part I: General theory, Interscience Publishers, New York, 1958.
[4] I. Franic, An extension theorem for bounded linear 2-functionals and applications, Math. Japonica 40(1994), 79-85.
[5] S. Gahler, 2-Metrische Raume and ihre Topologische Struktur, Math. Nachr. 26 (1963/64), 115-148.
[6] S. Gahler, Linear 2-Normierte Raume, Math. Nachr. 28 (1965), 1-45.
[7] S. Gahler, Uber 2-Banach-Raume, Math. Nachr. 42 (1969),, 335-347.
[8] T.L. Hayden, The extension of bilinear funcitonals, Pacific, J. Math. 22 (1967), 99-108.
[9] R.B. Holmes, On the continuity of best approximaiton operators, inSymposium on Infinite Dimensional Topology (R.D. Anderson Editor), Annals of Math. Studies, Princeton Univ. Press, Princeton 1972, 137-158.
[10] R.B. Holmes, Geometric Functional Analysis and its Application, Springer-Verlag, Berlin 1975.
[11] K. Iseki, Mathematics on 2-normed spaces, Bull. Korean, Math. Soc., 13 (1976), 127-136.
[12] L.Lindenstrauss, Extension of compact operators, Mem. Amer. Math.Soc. 48 (1964)
[13] S. Mabizela, On bounded 2-linear fucntionals, Math. Japonica, 35 (1990), 51-55.
[14] K. Nachbin, A theorem of Hahn-Banach type for linear transformation, Trans. Amer. Math. Soc., 68 (1950), 28-46.
[15] L. Nachnin, Some problems in extending and lifting continuous linear transformations, in Proc.International symposium on Linear Spaces, Jerusalem, 1960.
[16] R.R. Phelps, Uniquencess of Hahn-Banach extension and unique best approximaiton, Trans. Amer. Math. Soc., 95 (1960), 238-255.
[17] I. Singer, Best Approximation in Normed Linear Spaces by Elements of Linear Subspaces, Publishing House of the Romanian Academy and Springer Verlag, Bucharest and Berlin, 1970.
[18] A.G. White Jr., 2-Banach spaces, Math. Nachr., 42 (1969), 43-60.
[19] A.G. White and Yeol Je Cho, Linear mappings on linear 2-normed spaces, Bull. Korean Math. Soc. 21 (1984), 1-6.
