Stability of the scalar potential and symmetry breaking in the economical 3-3-1 model Yithsbey Giraldo, William A. Ponce and Luis A. Sánchez Eur. Phys. J. C, 63 3 (2009) 461-475 Published online: 31 July 2009 DOI: 10.1140/epjc/s10052-009-1101-4