1. Alonso, J., Martini, H., Wu, S.: On Birkhoff orthogonality and isosceles orthogonality in normed linear spaces. Aequationes Math. 83, 153–189 (2012)
2. Alonso, J., Martini, H., Wu, S.: Orthogonality types in normed linear spaces. In: Papadopoulos, A. (ed.) Surveys in Geometry I, 97–170. Springer, Cham (2022)
3. Birkhoff, G.: Orthogonality in linear metric spaces. Duke Math. J. 1, 169–172 (1935)
4. Chmieliński, J.: On an $$\varepsilon $$-Birkhoff orthogonality. J. Inequal. Pure Appl. Math. 6, 79 (2005)
5. Chmieliński, J.: Approximate Birkhoff-James orthogonality in normed linear spaces and related topics. In: Aron, R.M., Moslehian, M.S., Spitkovsky, I.M., Woerdeman, H.J. (eds.) Operator and Norm Inequalities and Related Topics, 303–320. Birkhäuser, Cham (2022)