Building a Premier Internship Program: A practical guide for Employers by Julie Cunningham from the National Association of Colleges and Employers (NACE).
Available for $79.00 (plus taxes and shipping) from http://naceweb.org/store.aspx.
The Ultimate Internship Guide for Employers from Employers Resource. Available as a free e-book from http://resources.employersresource.com/ultimate-internship-guide-for-employers.
The Complete Intern Compensation Guide from Looksharp.com. Available as a free e-book from https://www.internmatch.com/guides/everything-you-need-to-know-about-intern-compensation.