@article {8971,
	title = {Phyletic relationships of protein structures based on spatial preference of residues},
	journal = {Journal of Molecular Evolution},
	year = {1993},
	pages = {67-78},
	doi = {10.1007/BF02407306},
	url = {http://www.ncbi.nlm.nih.gov/pubmed/8381879},
	author = {Chun-xu Qu and Lu-Hua Lai and Xiao-jie Xu and You-qi Tang}
}
