re-motion API documentation is part of the source code itself
and generated with NDoc (a .chm file)
You can download the version for re-motion 1.13.6., the one
you currently need for the PhoneBook tutorial, here:
http://re-motion.org/community/LinkClick.aspx?fileticket=Z1ruZwb6DgQ%3d&tabid=69
For other versions of re-motion, the corresponding version is
always part of the binary distribution.