more fixes from PR feedback

overview.md

@@ -21,8 +21,8 @@ JSON Schemas provide the core testing definitions, and are used in an array of v
 on [RFC 8288 (Web Linking)](https://tools.ietf.org/rfc/rfc8288.txt) to express relationships between resources,
 and IANA [Media Types](https://en.wikipedia.org/wiki/Media_type) to describe file formats and format contents.
 The [OGC API - Features](https://ogcapi.ogc.org/features/) standard is a final core building block. The STAC
-Collection extends their [Collection](http://docs.opengeospatial.org/is/17-069r3/17-069r3.html#_collection_)
-JSON (and the full API is the foundation for the STAC API specification).
+Collection extends the [Collection](http://docs.opengeospatial.org/is/17-069r3/17-069r3.html#_collection_)
+JSON defined in OGC API - Features (and the full API definition is the foundation for the STAC API specification).
 
 The STAC specifications are written to be understandable without needing a full background in these. But if you 
 want to get deep into STAC tool implementation and are not familiar with any of the standards mentioned above it is