@book{ BA01552731, author = "Jennings, R. Y. (Robert Yewdall) and Spencer, J. R.", title = "What is international law and how do we tell it when we see it ?", publisher = "Kluwer", year = "1983", series = "The Cambridge-Tilburg law lectures", number = "3rd ser., 1980", URL = "https://ci.nii.ac.jp/ncid/BA01552731" }