(1)
Andrij Rovenchak, Effective Hamiltonian and excitation spectrum of harmonically trapped bosons: Бозе-эйнштейновская конденсация, Low Temp. Phys. 42, (2015) [Fiz. Nizk. Temp. 42, 49-55, (2015)] DOI: https://doi.org/10.1063/1.4939154 .