{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,20]],"date-time":"2026-04-20T17:11:04Z","timestamp":1776705064858,"version":"3.51.2"},"reference-count":22,"publisher":"Wiley","issue":"1","license":[{"start":{"date-parts":[[2023,5,31]],"date-time":"2023-05-31T00:00:00Z","timestamp":1685491200000},"content-version":"vor","delay-in-days":119,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"DOI":"10.13039\/501100016047","name":"Science Fund of the Republic of Serbia","doi-asserted-by":"publisher","award":["6062228"],"award-info":[{"award-number":["6062228"]}],"id":[{"id":"10.13039\/501100016047","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Mathematical Logic Qtrly"],"published-print":{"date-parts":[[2023,2]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>In this paper we start the analysis of the class , the class of cofinal types of directed sets of cofinality at most \u2135<jats:sub>2<\/jats:sub>. We compare elements of  using the notion of Tukey reducibility. We isolate some simple cofinal types in , and then proceed to find some of these types which have an immediate successor in the Tukey ordering of .<\/jats:p>","DOI":"10.1002\/malq.202200021","type":"journal-article","created":{"date-parts":[[2023,6,1]],"date-time":"2023-06-01T05:25:20Z","timestamp":1685597120000},"page":"92-103","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Cofinal types on \u03c9<sub>2<\/sub>"],"prefix":"10.1002","volume":"69","author":[{"given":"Borisa","family":"Kuzeljevic","sequence":"first","affiliation":[{"name":"Department of Mathematics and Informatics University of Novi Sad Serbia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Stevo","family":"Todorcevic","sequence":"additional","affiliation":[{"name":"Department of Mathematics University of Toronto Canada"},{"name":"Institut de Math\u00e9matiques de Jussieu UMR 7586 France"},{"name":"Mathematical Institute SANU Serbia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2023,5,31]]},"reference":[{"key":"e_1_2_9_2_1","doi-asserted-by":"publisher","DOI":"10.2307\/1968508"},{"key":"e_1_2_9_3_1","doi-asserted-by":"publisher","DOI":"10.1215\/S0012-7094-44-01119-1"},{"issue":"3","key":"e_1_2_9_4_1","first-page":"907","article-title":"Tukey types of ultrafilters","volume":"55","author":"Dobrinen N.","year":"2013","journal-title":"Illinois J. 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