{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,29]],"date-time":"2026-04-29T15:13:18Z","timestamp":1777475598356,"version":"3.51.4"},"reference-count":0,"publisher":"Walter de Gruyter GmbH","issue":"2","license":[{"start":{"date-parts":[[2014,6,30]],"date-time":"2014-06-30T00:00:00Z","timestamp":1404086400000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2014,6,30]]},"abstract":"<jats:title>Summary<\/jats:title>\n                  <jats:p>This article provides a formalized proof of the so-called \u201cthe four-square theorem\u201d, namely any natural number can be expressed by a sum of four squares, which was proved by Lagrange in 1770. An informal proof of the theorem can be found in the number theory literature, e.g. in [14], [1] or [23].<\/jats:p>\n                  <jats:p>This theorem is item #19 from the \u201cFormalizing 100 Theorems\u201d list maintained by Freek Wiedijk at http:\/\/www.cs.ru.nl\/F.Wiedijk\/100\/.<\/jats:p>","DOI":"10.2478\/forma-2014-0012","type":"journal-article","created":{"date-parts":[[2015,2,5]],"date-time":"2015-02-05T08:48:28Z","timestamp":1423126108000},"page":"105-110","source":"Crossref","is-referenced-by-count":0,"title":["Lagrange\u2019s Four-Square Theorem"],"prefix":"10.2478","volume":"22","author":[{"given":"Yasushige","family":"Watase","sequence":"first","affiliation":[{"name":"Suginami-ku Matsunoki 6, 3-21 Tokyo, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"374","published-online":{"date-parts":[[2014,6,30]]},"container-title":["Formalized Mathematics"],"original-title":[],"language":"en","link":[{"URL":"http:\/\/content.sciendo.com\/view\/journals\/forma\/22\/2\/article-p105.xml","content-type":"text\/html","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/reference-global.com\/pdf\/10.2478\/forma-2014-0012","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T13:53:31Z","timestamp":1777384411000},"score":1,"resource":{"primary":{"URL":"https:\/\/reference-global.com\/article\/10.2478\/forma-2014-0012"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2014,6,30]]},"references-count":0,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2014,6,30]]},"published-print":{"date-parts":[[2014,6,30]]}},"alternative-id":["10.2478\/forma-2014-0012"],"URL":"https:\/\/doi.org\/10.2478\/forma-2014-0012","relation":{},"ISSN":["1898-9934"],"issn-type":[{"value":"1898-9934","type":"electronic"}],"subject":[],"published":{"date-parts":[[2014,6,30]]}}}