Studio Pottery Marks best book

Pretty sure that this has been asked before but what are the best book/books for Studio pottery marks?

thanks in advance

I think the online info has improved faster than the printed version and the best of all is being compiled by Naomi as we speak

The bible on British Studio Pottery Marks will always be the one by Yates & Fournier, which is now in its 3rd Edition.
http://pin.it/U1JqMNY
It has recently been remaindered by the publisher so you should be able to pick up a copy for under £20. If you don't want to spend that much then get the 2nd edition.

lovely job Naomi and Dan . thanks for your replies

just grabbed a 3rd edition for £19-99 so that should expand my limited knowledge

I got a copy of the 3rd edition last month for £12.49, by the time I spotted them the seller had upped the price by a tenner but they kindly agreed to do a discount and refunded me a tenner today