When applied properly, an SPF 15 filters out 93 percent of UVB, SPF 30 filters 97 percent and SPF 50 filters 98 percent. SPF 15 is good enough. According to The Skin Cancer Foundation, most sunscreens with an SPF of 15 or higher do an excellent job of protecting against UVB.PF10-15 is good enough for me as my skin is allergic to higher SPF for you need to add chemicals onto the product in order to achieve a higher SPF.
TEXTBOOK AND COURSE BOOK POLICY. Desk copies | Course use examination copies | Ordering | Course adopted books as electronic downloads . Desk Copies. Desk copies are complimentary books sent to professors who have already adopted the book for a course. To request a desk copy, professors can send an e-mail to our customer service vendor, the Chicago Distribution Center (CDC), at orders@press.uchicago.edu.
To request a desk copy, find the book on this website with the search functionality, and click on the request link in the lower left portion of the book page. Follow the instructions there. Some books, due to their wholesale discount, cannot be offered as textbook desk copies, so it is possible that even if these criteria are met we will not be able to provide one.