Dear Dr. Harkness, your "Solar radiation control in buildings" has been the book that I have opened many-many times during my academic work at the UK Architectural Association in the '80s.

I was impressed by the shading device optimization method that you described using descriptive geometry, a topic that I was teaching at the National Technical University of Athens when your book was published.

That method inspired me to devise an algorithm that I posted in the web in 2000 [ http://oikotekton.eu/shadecad/ ].

Currently I am writing a paper on a similar topic, and I wonder if you could be kind enough to allow me to use some illustrations from pp 187-234, with all proper references of course.

Thank you for your attention.

::: Thanos N. Stasinopoulos