@article{oai:tsukuba.repo.nii.ac.jp:00016021,
 author = {Jian-Ping, Zhu},
 issue = {1},
 journal = {Tsukuba Journal of Mathematics},
 month = {Jun},
 pages = {167--173},
 title = {The generalizations of first countable spaces},
 volume = {15},
 year = {1991}
}