Author,Title,Journal,ISSN,Publisher,Date,Volume,Number,Page,URL,URL(DOI) Elihu Lubkin,Entropy of an n-system from its correlation with a k-reservoir,Journal of Mathematical Physics,0022-2488,AIP Publishing,1978-05-01,19,5,1028-1031,https://cir.nii.ac.jp/crid/1360574095062080896,https://doi.org/10.1063/1.523763