It is required to use the terms clause and annex where applicable. It is unnecessary to use the term "subclause".
If there is a need to refer to an unnumbered list item in another standard, the following formulation shall be used:
"as specified in 3.1, second list item".
Lower case letters are recommended (e.g. clause 1, annex A), however capital letters are also acceptable (e.g. Clause 1, Annex A). Usage should be consistent throughout the document.