Where is $ref allowed in OpenAPI 3.0 specification?

For our development purposes we often need to reuse definitions as much as possible from a linked specification document.

However Swagger's OpenAPI 3.0 documentation only says the following:

A common misconception is that $ref is allowed anywhere in an OpenAPI specification file. Actually $ref is only allowed in places where the OpenAPI 3.0 Specification explicitly states that the value may be a reference. For example, $ref cannot be used in the info section and directly under paths

and the link to specification is, of course, a generic one.

So, I am wondering - is there a list compiled by someone - where specifically using $ref is allowed?