text: Cimiano P, Völker J. Text2Onto. Natural Language Processing and Information Systems. Berlin, Heidelberg: Springer Berlin Heidelberg; 2005.p. 227-238. ISBN: 978-3-540-32110-1 
  Drymonas E, Zervanou K, Petrakis EGM. Unsupervised Ontology Acquisition from Plain Texts: The OntoGain System. Natural Language Processing and Information Systems. Berlin, Heidelberg: 
  Springer Berlin Heidelberg; 2010. p. 277-87. ISBN: 978-3-642-13881-2 
  Paola Velardi, Stefano Faralli, Roberto Navigli; OntoLearn Reloaded: A Graph-Based Algorithm for Taxonomy Induction. Computational Linguistics 2013; 39 (3): 665–707. DOI: 
  10.1162/COLI_a_00146 
  Muhammad Nabeel Asim, Muhammad Wasim, Muhammad Usman Ghani Khan, Waqar Mahmood, Hafiza Mahnoor Abbasi, A survey of ontology learning techniques and applications, 
  Database, Volume 2018, 2018, bay101, DOI: 10.1093/database/bay101 