Update versions/3.1.1.md

Author: ralfhandl

versions/3.1.1.md

@@ -124,7 +124,7 @@ In order to preserve the ability to round-trip between YAML and JSON formats, YA
 An OpenAPI Description (OAD) MAY be made up of a single document or be divided into multiple, connected parts at the discretion of the author. In the latter case, [Reference Object](#reference-object), [Path Item Object](#path-item-object) and [Schema Object](#schema-object) `$ref` keywords, as well as the [Link Object](#link-object) `operationRef` keyword, are used.
 
 Any document consisting entirely of an [OpenAPI Object](#openapi-object) is known as a **syntactically complete OpenAPI document**.
-An OpenAPI document that does ***not*** reference any other documents is known as a **self-contained OpenAPI document.***
+An OpenAPI document that does _not_ reference any other documents is known as a **self-contained OpenAPI document**.
 A single-document description is therefore _both_ syntactically complete _and_ self-contained.
 In a multi-document description, the document containing the OpenAPI Object where parsing begins for a specific API's description is known as that API's **entry OpenAPI document**, or simply **entry document**.