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Table of Formal and Descriptivists Ontologists (PDF - from Bernard Bolzano to present time)
Ontologists of the 19th and 20th Centuries (a selection of critical judgments about some of the greatest philosophers of the recent past)
Living Ontologists (a list of authors with an interest in ontology, with synthetic Bibliographies)
Dombrowski, Dan, "Charles Hartshorne", The Stanford Encyclopedia of Philosophy (Fall 2011 Edition) , Edward N. Zalta (ed.)
Charles Hartshorne: Primary Bibliography of Philosophical Works by Dorothy C. Hartshorne