Exact chapter in ISO 15930-1:2001 (PDF/X-1a)

Hi,

Silly question perhaps, but which part of ISO 15930-1:2001 (PDF/X-1a) precisely tells me that new PDF-features like Live Transparency (PDF 1.4), Optional content (PDF1.5) are not allowed. Not that I doubt that it is prohibited. But I need to pinpoint the exact chapter / paragraph in the PDF/X-1a spec telling me that.

Thanks