@book{
  international1991iaea,
  title={Grading of Quality Assurance Requirement},
  series={Technical Reports Series},
  number={328},
  year={1991},
  isbn={92-0-155291-2},
  url={https://www.iaea.org/publications/1432/grading-of-quality-assurance-requirement},
  publisher={INTERNATIONAL ATOMIC ENERGY AGENCY},
  address={Vienna}
}