Q. I need a template letter for requesting copyright permission to link to or reprint resources in a book or e-book

Here is a generic letter that you can adapt/edit for your purposes:
http://copyright.lib.utexas.edu/permmm.html

It isn't necessary for you to mail this letter, or for them to mail you a signed original copy in return - an email will suffice in both directions. It's also good to make it clear in the letter that you will give full attribution - something like "Full acknowledgement will be given to the rights holder."