Part 5: clarify normative reference to Part 1: Core

Author: cportele

extensions/schemas/standard/clause_3_references.adoc

@@ -7,6 +7,8 @@ The following normative documents contain provisions that, through reference in
 
 * [[OAFeat-1]] Open Geospatial Consortium (OGC). OGC 17-069r4: **OGC API - Features - Part 1: Core** [online]. Edited by C. Portele, P. Vretanos, C. Heazel. 2022 [viewed 2023-10-14]. Available at https://docs.ogc.org/is/17-069r4/17-069r4.html
 
+NOTE: OGC API - Features - Part 1: Core is a normative reference for the Abstract Test Suite only. It is not a dependency for the requirements classes defined in this Standard.
+
 * [[ogc06_103r4]] Open Geospatial Consortium (OGC). OGC 06-103r4: **OpenGIS® Implementation Standard for Geographic information - Simple feature access - Part 1: Common architecture**. Edited by J. Herring. 2011. Available at http://portal.opengeospatial.org/files/?artifact_id=25355
 
 * [[qudtunits]] QUDT.org. **QUDT Units Vocabulary 2.1**. Edited by R. Hodgson. 2024. Available at https://www.qudt.org/doc/DOC_VOCAB-UNITS.html.