I'm trying to find a definitive answer as to when you have to use the trademark symbol. I have always thought that you used the trademark symbol the first time a term appeared in context. Every other occurence of that word within the rest of the document did not need to carry the symbol, as it was covered by the first use.
I've recently picked up a client who has every occurence of thier trademark terms identified on every document. This is a visual nightmare, as you can immagine, and I would like to change this. I have been trying to find some actual literature regarding the proper use however I haven't found anything online, nor in my handy Bringhurst book.
Is there an actual rule? If so, what is it? Is there a book or official online document I could refer to?