{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,8]],"date-time":"2026-01-08T23:37:58Z","timestamp":1767915478933,"version":"3.49.0"},"reference-count":9,"publisher":"Elsevier BV","issue":"4","license":[{"start":{"date-parts":[[1981,11,1]],"date-time":"1981-11-01T00:00:00Z","timestamp":373420800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/www.elsevier.com\/tdm\/userlicense\/1.0\/"},{"start":{"date-parts":[[2013,7,17]],"date-time":"2013-07-17T00:00:00Z","timestamp":1374019200000},"content-version":"vor","delay-in-days":11581,"URL":"https:\/\/www.elsevier.com\/open-access\/userlicense\/1.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Discrete Applied Mathematics"],"published-print":{"date-parts":[[1981,11]]},"DOI":"10.1016\/0166-218x(81)90006-8","type":"journal-article","created":{"date-parts":[[2002,10,10]],"date-time":"2002-10-10T22:04:08Z","timestamp":1034287448000},"page":"289-299","source":"Crossref","is-referenced-by-count":5,"title":["Decidability and density in two-symbol grammar forms"],"prefix":"10.1016","volume":"3","author":[{"given":"H.A.","family":"Maurer","sequence":"first","affiliation":[]},{"given":"A.","family":"Salomaa","sequence":"additional","affiliation":[]},{"given":"D.","family":"Wood","sequence":"additional","affiliation":[]}],"member":"78","reference":[{"key":"10.1016\/0166-218X(81)90006-8_BIB1","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1016\/0304-3975(78)90005-1","article-title":"Two-symbol complete E0L forms","volume":"6","author":"Culik","year":"1978","journal-title":"Theoret. Comput. Sci"},{"key":"10.1016\/0166-218X(81)90006-8_BIB2","doi-asserted-by":"crossref","first-page":"110","DOI":"10.1016\/0022-0000(80)90045-8","article-title":"Context-free grammar forms with strict interpretations","volume":"21","author":"Maurer","year":"1980","journal-title":"J. Comput. System Sci"},{"key":"10.1016\/0166-218X(81)90006-8_BIB3","series-title":"Report 80-CS-20, Unit for Computer Science","article-title":"A super normal form theorem for context-free grammars","author":"Maurer","year":"1980"},{"key":"10.1016\/0166-218X(81)90006-8_BIB4","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1016\/0304-3975(80)90026-2","article-title":"Synchronized E0L forms","volume":"12","author":"Maurer","year":"1980","journal-title":"Theoret. Comput. Sci"},{"key":"10.1016\/0166-218X(81)90006-8_BIB5","article-title":"Dense hierarchies of grammatical families","author":"Maurer","year":"1981","journal-title":"J. Assoc. Comput. Mach"},{"key":"10.1016\/0166-218X(81)90006-8_BIB6","doi-asserted-by":"crossref","first-page":"187","DOI":"10.1016\/S0019-9958(80)90758-5","volume":"46","author":"Maurer","year":"1980","journal-title":"MSW spaces, Information and Control"},{"key":"10.1016\/0166-218X(81)90006-8_BIB7","doi-asserted-by":"crossref","first-page":"184","DOI":"10.1016\/0020-0190(81)90097-1","article-title":"Sub-regular grammar forms","volume":"12","author":"Ottmann","year":"1981","journal-title":"Inform. Process. Lett"},{"key":"10.1016\/0166-218X(81)90006-8_BIB8","series-title":"The Mathematical Theory of L Systems","author":"Rozenberg","year":"1980"},{"key":"10.1016\/0166-218X(81)90006-8_BIB9","article-title":"Grammar and L Forms: An Introduction","volume":"Vol. 91","author":"Wood","year":"1980"}],"container-title":["Discrete Applied Mathematics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/api.elsevier.com\/content\/article\/PII:0166218X81900068?httpAccept=text\/xml","content-type":"text\/xml","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/api.elsevier.com\/content\/article\/PII:0166218X81900068?httpAccept=text\/plain","content-type":"text\/plain","content-version":"vor","intended-application":"text-mining"}],"deposited":{"date-parts":[[2019,4,13]],"date-time":"2019-04-13T21:23:16Z","timestamp":1555190596000},"score":1,"resource":{"primary":{"URL":"https:\/\/linkinghub.elsevier.com\/retrieve\/pii\/0166218X81900068"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1981,11]]},"references-count":9,"journal-issue":{"issue":"4","published-print":{"date-parts":[[1981,11]]}},"alternative-id":["0166218X81900068"],"URL":"https:\/\/doi.org\/10.1016\/0166-218x(81)90006-8","relation":{},"ISSN":["0166-218X"],"issn-type":[{"value":"0166-218X","type":"print"}],"subject":[],"published":{"date-parts":[[1981,11]]}}}