Approximate bound state solutions of the Klein-Gordon equation with the linear combination of Hulthén and Yukawa potentials
A.I. Ahmadov, S.M. Aslanova, M.S. Orujova, S.V. Badalov, S.-H. Dong, Physics Letters A 383 (2019) 3010–3017.

Annihilation of delocalized positrons: a comparison of diamond and silicon
W.G. Schmidt, W.S. Verwoerd, Physics Letters A 222 (1996) 275–280.