@article{oai:tsukuba.repo.nii.ac.jp:00015774,
 author = {Ochiai, Shoji},
 issue = {1},
 journal = {Tsukuba Journal of Mathematics},
 month = {Jun},
 pages = {63--74},
 title = {On a topological invariant of finite topological spaces and enumerations},
 volume = {16},
 year = {1992}
}