For learn, y suggest :
Fundamentals: Building Visual Studio Applications on a Visual FoxPro 6.0

And after they can read:
Effective Techniques for Application Development with Visual FoxPro 6.0
1001 Things You Wanted to Know About Visual FoxPro

If they need most level:

Client-Server Applications with Visual FoxPro and SQL Server 7.0
Advanced Object Oriented Programming with Visual FoxPro 6.0
Visual FoxPro Certification Exams Study Guide

and then substitute the VFP Help with CHM version off "Hackers"

Regards,
José Luis.