@article{articled092214e,
title   = {Mass perturbation around the exact solution of a two-dimensional field-theoretical model},
author = {Afioni, M. El and Gomes, Marcelo Otávio Caminha and Koberle, Roland},
year = {1979},
doi = {10.1103/PhysRevD.19.1791},
journal   = {Physical Review D}
}