Using Customer Inquiries as a Basis for Revising and Editing User Manuals 
The Documentation Development Department (DDD) of Hitachi has been improving manuals by collecting, classifying, and analyzing inquiries from its customers to the Hitachi Customer Answer (HCA) Center. The HCA Center is a telephone inquiry center established to give quick and clear answers to inquiries from customers who use Hitachi computers.
Masuda, Tadashi. STC Proceedings (1994). Articles>Documentation>User Centered Design