Both books that Norm mentioned are good books to read and use to understand "square rule" joinery.
They are available from the guild at the online store. If you go to the guild home page and click on the "Online Store" link then select "publications", they are there for you to buy.
Also another site is Summer Beam books here:
Link to Summer Beam Books site and then select timber framing in the category section. The timber framing section will list a lot of books. One of them is:
THE SCRIBE RULE OR THE SQUARE RULE: TRADITIONAL TIMBER FRAME LAYOUT SYSTEMS
A discussion and explanation of the two methods of timber framing layout.
Pages 17
$6.00 spiral by Jack Sobon.
Enjoy your reading. Jim