Here are some sources of valuable guidance on project quality assurance. We provide links to the material itself for material with no copyright protection otherwise we provide links to the organisation's website:
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For projects in the Government Sector, the GCDO's System Assurance guidance:
​www.digital.govt.nz/standards-and-guidance/governance/system-assurance

Also for projects in the Government Sector, The Treasury's Investment Management site:
www.treasury.govt.nz/statesector/investmentmanagement 

The Association for Project Management, the UK chartered body for the project profession:
"A Guide to Integrated Assurance"
www.apm.org.uk/book-shop/a-guide-to-integrated-assurance/