@article{article02d0daf5,
title   = {Approximate controllability of second-order distributed implicit functional systems},
author = {Henriquez, Hernán R. and Morales, Eduardo Alex Hernández},
year = {2009},
doi = {10.1016/j.na.2008.01.029},
journal   = {Nonlinear Analysis: Theory, Methods & Applications}
}