@article{11069,
  author = {S. Borowitz and E. Gerjuoy},
  title = {Variational Principles and Perturbation Theory},
  year = {1965},
  number = {36},
  pages = {1-52},
  month = {1965-05},
  address = {Boulder},
  issn = {36},
  note = {JILA Pub. 84},
}