[1] Chakalov V.L.: 
Extremal elements in some normed spaces. Comptes Rendus Acad. Bulgare des Sciences 36 (1983), 173-176. 
MR 0709005[2] Cobzaş S.: 
Very non-proximinal sets in $c_0$ (in Romanian). Rev. Anal. Numer. Teoria Approx. 2 (1973), 137-141. 
MR 0393980[3] Cobzaş S.: 
Antiproximinal sets in some Banach spaces. Math. Balkanica 4 (1974), 79-82. 
MR 0377381[4] Cobzaş S.: 
Convex antiproximinal sets in the spaces $c_0$ and $c$ (in Russian). Matem. Zametki 17 (1975), 449-457. 
MR 0407567[5] Cobzaş S.: 
Antiproximinal sets in Banach spaces of continuous functions. Anal. Numér. Théorie Approx. 5 (1976), 127-143. 
MR 0477577[6] Cobzaş S.: 
Antiproximinal sets in Banach spaces of $c_0$-type. Rev. Anal. Numér. Théorie Approx. 7 (1978), 141-145. 
MR 0530744[7] Cobzaş S.: Support functionals of the unit ball in Banach spaces of bounded functions. Seminar on Mathematical Analysis, Babeş-Bolyai University Research Seminaries, Preprint nr. 4, pp.85-90, Cluj-Napoca, 1986.
[8] Dunford N., Schwartz J.T.: 
Linear Operators I. General Theory. Interscience, New York, 1958. 
MR 0117523 | 
Zbl 0084.10402[9] Edelstein M., Thompson A.C.: 
Some results on nearest points and support properties of convex sets in $c_0$. Pacific J. Math. 40 (1972), 553-560. 
MR 0308741[10] Fonf V.P.: 
On antiproximinal sets in spaces of continuous functions on compacta (in Russian). Matem. Zametki 33 (1983), 549-558. 
MR 0704442[11] Fonf V.P.: 
On strongly antiproximinal sets in Banach spaces (in Russian). Matem. Zametki 47 (1990), 130-136. 
MR 1048552[12] Holmes R.B.: 
Geometric Functional Analysis and its Applications. Springer Verlag, BerlinHeidelberg-New York, 1975. 
MR 0410335 | 
Zbl 0336.46001[13] Klee V.: 
Remarks on nearest points in normed linear spaces. Proc. Colloq. Convexity, Copenhagen 1965, pp.161-176, Copenhagen, 1967. 
MR 0223859 | 
Zbl 0156.36303[14] Phelps R.R.: 
Subreflexive normed linear spaces. Archiv der Math. 8 (1957), 444-450. 
MR 0099588[17] Singer I.: 
Best Approximation in Normed Linear Spaces by Elements of Linear Subspaces. Editura Academiei and Springer Verlag, Bucharest-Berlin, 1970. 
MR 0270044 | 
Zbl 0197.38601[18] Stečkin S.B.: 
On the approximation properties of sets in normed linear spaces (in Russian). Rev. Math. Pures et Appl. 8 (1963), 5-18. 
MR 0155168[19] Zukhovickij S.I.: 
On minimal extensions of linear functionals in spaces of continuous functions (in Russian). Izvestija Akad. Nauk SSSR, ser. matem. 21 (1957), 409-422. 
MR 0088702