CSIRT Maturity Kit
https://check.ncsc.nl/static/CSIRT_MK_guide.pdf

FIRST Security Reference Index
https://first.org/resources/guides/reference

FIRST CSIRT Services Framework
https://www.first.org/_assets/global/first-csirt-services-education-framework-first-final-draft.pdf

Global Forum on Cyber Expertise
https://www.thegfce.com/