REFERENCES
[1] E. Asplund and B. Gr¨unbaum, On the geometry of Minkowski planes, Eins. Math. 6 (1960), 299-306.
[2] B. Bagchi, G. Misra and N.S.N. Sastry (problem proposed by): Coverup Revealed in Hilbert
spaces (Advanced Problem 6577), Amer. Math. Monthly 97 (1990), 936-937.
[3] A. Bezdek, On a generalization of Tarski’s plank problem, Discrete Comput. Geom. 38 (2007), 189-200.
[4] K. B¨or¨oczky, Finite packing and covering, Cambridge University Press, Cambridge, 2004.
[5] B. Carl and D.E. Edmunds, Gelfand numbers and metric entropy of convex hulls in Hilbert
spaces, Studia Math. 159 (2003), 391-402.
[6] M. Cavachi (problem proposed by): The plane covered by disks, Problems and solutions, Amer.
Math. Monthly 106 (1999), 364-365.
[7] L.X. Cheng, Ball-covering property of Banach spaces, Israel J. Math. 156 (2006), 111-123.
[8] L.X. Cheng, Q.J. Cheng and X.Y. Liu, Ball-covering property of Banach spaces that is not
preserved under linear isomorphisms, Sc. China Ser.A: Math. 51 (2008), 143-147.
[9] V.P. Fonf and C. Zanco, Covering spheres of Banach spaces by balls, Math. Ann. to appear.
[10] R.Y. Fu and L.X. Cheng, Ball-coverings property of Banach spaces (Chinese), J. Math. Study
39 (2006), 39-43.
[11] M. Furi and A. Vignoli, On a property of the unit sphere in a linear normed space, Bull. Acad.
Polon. Sc. S´er. Sc. Math. Astr. Phys. 18 (1970), 333-334.
[12] A. Hinrichs and C. Richter, New sets with large Borsuk numbers, Discrete Math. 270 (2003),
137-147.
[13] A. Hinrichs and C. Richter, Tilings, packings, coverings, and the approximation of functions,
Math. Nachr. 267 (2004), 37-45.
[14] V.M. Kadets, Weak cluster points of a sequence and coverings by cylinders, Mat. Fiz. Anal.
Geom. 11 (2004), 161-168.
[15] V.M. Kadets, Coverings by convex bodies and inscribed balls, Proc. Amer. Math. Soc. 133
(2005), 1491-1495.
[16] L. Lyusternik and L. Sˇnirel’man, Topological methods in variational problems and their application
to the differential geometry of surfaces (Russian), Uspehi Matem. Nauk (N.S.) 2 (1947),
no.1 (17), 166-217.
[17] E. Maluta and P.L. Papini, Relative centers and finite nets for the unit ball and its finite subsets,
Boll. Un. Mat. Ital. 7 (1993), 451-472.
[18] E. Maluta and P.L. Papini, Estimates for Kottman’s separation constant in reflexive Banach
spaces, Colloq. Math., to appear.
[19] I. Moln´ar, Citeva probleme nerezolvate de geometrie (Romanian), Gaz. Mat. Fiz. Ser. A 10
(63) (1958), 730-735.
[20] P.L. Papini, Some parameters of Banach spaces, Rend. Sem. Mat. Fis. Milano 53 (1983), 131-
148.
[21] P. Schmitt, Problems in discrete and computational geometry, in: Handbook of convex geometry
(P.M. Gruber and J.M. Wills editors), North-Holland, Amsterdam 1993; 449-483.
[22] H.H. Shi and X.J. Zhang, Minimal ball covering of the unit sphere in Rn (Chinese), Xiamen
Daxue Xuebao Ziran Kexue Ban 45 (2006), 621-623.
[23] R. Whitley, The size of the unit sphere, Canad. J. Math. 20 (1968), 450-455.
[24] X.J. Zhang, Radius of a minimal ball-covering in the space Rn (Chinese), J. Math. Study 40
(2007), 109-113