@article{oai:soar-ir.repo.nii.ac.jp:00018383,
 author = {Futa, Yuichi and Okazaki, Hiroyuki and Shidama, Yasunari},
 issue = {4},
 journal = {Formalized Mathematics},
 month = {Dec},
 note = {Article, Formalized Mathematics. 21(4): 273-282 (2013)},
 pages = {273--282},
 title = {Submodule of free Z-module},
 volume = {21},
 year = {2013}
}