What is DoI?

Some articles on doi:

Symposium On Theory Of Computing - References
... Cook, Stephen (1971), "The complexity of theorem proving procedures", Proc ... STOC 1971, pp ...
Stephen Arthur Jennings - Selected Bibliography
... Chang, Bomshik Jennings, S ... A Ree, Rimhak (1958), "On certain pairs of matrices which generate free groups", Canadian Journal of Mathematics 10 (0) 279–284, doi10.4153/CJM-1958-029-2, ISSN 0008-414X, MR0094388 Jennings, S ...
Masaki Doi
... Masaki Doi (土井 真樹, Doi Masaki?, born July 7, 1960) is a Japanese politician serving in the House of Representatives in the Diet (national legislature ...