It seems the current version of Newton don't have the type NewtonContact at all, and the contact callback type is named NewtonContactsProcess.
But in the list page of API database http://newtondynamics.com/wiki/index.php5?title=API_Database#Callbacks, it still lists the old callback type NewtonContactProcess, and it still type of NewtonContact as argument.
And could there has a downloadable version of API documents?