For citations:
Albeverio S., Fassari S., Rinaldi F. The behaviour of the three-dimensional Hamiltonian −∆ + λ [δ(x + x0) + δ(x − x0)] as the distance between the two centres vanishes. Nanosystems: Physics, Chemistry, Mathematics. 2017;8(2):153-159. https://doi.org/10.17586/2220-8054-2017-8-2-153-159