Sutherland, W. R., On-Line Graphical Specification of
Computer Procedures,
M.I.T. Lincoln Lab., Tech. Report No. 405, Lexington, Mass. (May, 1966).
It is available as Ph.D. at "http://theses.mit.edu".
I downloaded it with wget as gif images through the "Overview of
thumbnail pages" service. No need to buy it.
Wait! It disables the access if you use wget.
The thesis is at
ftp://ftp.funet.fi/pub/sci/audio/devel/dsp/
for your convenience.
Juhana