@article{andrews_meath_1993, 
  title={On the role of permanent dipoles in second harmonic generation}, 
  volume={26}, 
  DOI={10.1088/0953-4075/26/23/030}, 
  number={23}, 
  publisher={IOP Publishing}, 
  author={Andrews and Meath}, 
  year={1993}, 
  month={Dec}
  }