Thanks for reaching out - I've just looked into this resource, and unfortunately it is no longer available. However, we have a whole community base that is willing to help with any questions you might have!
If you do run into an article/resource you think you should have access to (but don't) we've been advised to send an email request to the following:
Include your status (i.e. partner, customer, etc) and the link to the resource you're trying to access. I've run into a few where the permissions are just messed up and the nice folks on the other end of that email have resolved the issue for me...