References
- Franchetti C, Furi M. Some characteristic properties of real Hilbert spaces. Rev Roumaine Math Pures Appl. 1972;17:1045–1048.
- Narang TD. On best coapproximation in normed linear spaces. Rocky Mt J Math. 1992;22(1):265–287.
- Papini PL, Singer I. Best coapproximation in normed linear spaces. Monatsh Fur Math. 1979;88(1):27–44.
- Rao GS, Swaminathan M. Best coapproximation and Schauder bases in Banach spaces. Acta Sci Math. 1990;54:339–354.
- Sain D, Sohel S, Ghosh S, et al. On best coapproximations in subspaces of diagonal matrices. Linear Multilinear Algebra. doi: 10.1080/03081087.2021.2017835
- Lewicki G, Trombetta G. Optimal and one-complemented subspaces. Monatsh Math. 2008;153(2):115–132.
- Birkhoff G. Orthogonality in linear metric spaces. Duke Math J. 1935;1:169–172.
- James RC. Orthogonality and linear functionals in normed linear spaces. Trans Amer Math Soc. 1947;61(2):265–292.
- Sain D. On best approximations to compact operators. Proc Amer Math Soc. 2021;149(10):4273–4286.