@article{
  author = {Ahmadian, M.T, Mojahedi, M, Moeenfard, H},
  title = {Free Vibration Analysis of a Nonlinear Beam Using Homotopy and Modified Lindstedt-Poincare Methods},
  journal = {Journal of Solid Mechanics},
  year = {2009},
  volume = {1},
  number = {1},
  pages = {29-36},
  doi = {}
}