Callan Publishing now offers official (PDF-like formats with DRM protection) through accredited online schools. You cannot buy these on Amazon or Google Books directly. You must either:
However, you can adapt. Here is a protocol for solo learners using Book 10: callan method book 10 pdf
The use of "will" vs. "to be going to" and the emphatic use of "to do" to deny previous statements. Thematic Topics: Callan Publishing now offers official (PDF-like formats with