diff --git a/src/cco-modules/AgentOntology.ttl b/src/cco-modules/AgentOntology.ttl
index fa32224..bd8ee66 100644
--- a/src/cco-modules/AgentOntology.ttl
+++ b/src/cco-modules/AgentOntology.ttl
@@ -1147,8 +1147,8 @@ cco:ActionRequirement rdf:type owl:Class ;
 ###  http://www.ontologyrepository.com/CommonCoreOntologies/Affordance
 cco:Affordance rdf:type owl:Class ;
                rdfs:subClassOf obo:BFO_0000017 ;
-               cco:definition "A Realizable Entity of an Independent Continuant that creates an opportunity for an Agent to realize some Capability or Disposition in some Act."@en ;
-               cco:definition_source "https://en.wikipedia.org/w/index.php?title=Affordance&oldid=1061963879"^^xsd:anyURI ;
+               cco:definition "A Realizable Entity of an Independent Continuant that is used by an Agent to realize some Agent Capability or Disposition in some Act."@en ;
+               cco:definition_source "J. J. Gibson, \"The Theory of Affordances,\" in The Ecological Approach to Visual Perception (NY: Taylor & Francis Group, 1986): 127-143. Available at: https://archive.org/details/pdfy-u5hmFOvOM2Civ4Gz/page/n70/mode/1up."@en ;
                cco:is_curated_in_ontology "http://www.ontologyrepository.com/CommonCoreOntologies/Mid/AgentOntology"^^xsd:anyURI ;
                rdfs:label "Affordance"@en .