@article{richardson_child_lever_1993, 
  title={Packaging of human immunodeficiency virus type 1 RNA requires cis-acting sequences outside the 5' leader region.}, 
  volume={67}, 
  DOI={10.1128/jvi.67.7.3997-4005.1993}, 
  publisher={American Society for Microbiology}, 
  author={Richardson, J H and Child, L A and Lever, A M}, 
  year={1993}
  }