Certification
IAPP article: 4 GDPR-certification myths dispelled (EN)
EDPB (European Data protection Board)
GDPR docs: https://edpb.europa.eu/node/28
ENISA
Interplay between standardisation and the General Data Protection Regulation: https://www.enisa.europa.eu/events/enisa-cscg-2017/presentations/kamara
Recommendations on European Data Protection Certification