About the author, AT:
 
Emeritus professor (PHD)
greatly aged, around 80.
(The initials AT come from 80. Call me Mr. Eighty, if needed)

The author's adress is ok.ia555z@gmail.com. 
Please replace 555 by 894.

If you send a polite e-mail and don't get a reply, 
don't assume I'm ignoring you. 
I may have been too busy to respond at the time 
or I may have planned to respond after doing some work.