® versus TM and SM: A Guide To Proper Trademark Use

If you’re unclear about when to use ®, ™ and other trademark identifiers, have a look at “A Guide to Proper Trademark Use” a brief Web page by Gregory H. Guillot, at http://www.ggmark.com/guide.html.

A more in-depth (but still clear) explanation comes from Crestron at http://www.crestron.com/downloads/pdf/misc/guide_to_trademark_use.pdf.