(a) Where any document cited in the international search report is of particular relevance, the special indication required by Rule 43.5(c) shall consist of the letter(s) "X" and/or "Y" placed next to the citation of the said document.
(b) Category "X" is applicable where a document is such that when taken alone, a claimed invention cannot be considered novel or cannot be considered to involve an inventive step.
(c) Category "Y" is applicable where a document is such that a claimed invention cannot be considered to involve an inventive step when the document is combined with one or more other such documents, such combination being obvious to a person skilled in the art.