@article{articled15dd3c6,
title   = {Singularity structure of the hopf bifurcation surface of a differential equation with two delays},
author = {Ragazzo, Clodoaldo Grotta and Malta, Coraci Pereira},
year = {1992},
doi = {10.1007%2FBF0104826},
journal   = {Journal of Dynamics and Differential Equations}
}