Just a quick heads-up for ACG: the link behind the "AWS Multi-Account Security Strategy" white paper actually points to the Billing Strategy one. Although they complement each other, they focus on different things, so the link should be updated to https://d1.awsstatic.com/aws-answers/AWS_Multi_Account_Security_Strategy.pdf.
Thanks for pointing this out. I have passed to on to ACG content team for review.
This is fixed up now, thanks!