Update versions/3.0.4.md

Author: ralfhandl

versions/3.0.4.md

@@ -121,7 +121,7 @@ In order to preserve the ability to round-trip between YAML and JSON formats, YA
 
 ### OpenAPI Description Structure
 
-An OpenAPI Description (OAD) MAY be made up of a single JSON or YAML document or be divided into multiple, connected parts at the discretion of the author. In the latter case, [Reference Object](#reference-object) and [Path Item Object](#path-item-object) `$ref` keywords, as well as the [Link Object](#link-object) `operationRef` keyword, and the URI form of the [Discriminator Object](#discriminator-object) mapping keyword, are used to identify the referenced elements.
+An OpenAPI Description (OAD) MAY be made up of a single JSON or YAML document or be divided into multiple, connected parts at the discretion of the author. In the latter case, [Reference Object](#reference-object) and [Path Item Object](#path-item-object) `$ref` fields, as well as the [Link Object](#link-object) `operationRef` field, and the URI form of the [Discriminator Object](#discriminator-object) `mapping` field, are used to identify the referenced elements.
 
 In a multi-document OAD, the document containing the OpenAPI Object where parsing begins is known as that OAD's **entry document**.