July 5, 1960
Dear Van:
It was very kind of you to send me your latest modification of the DNA model.  I have had a chance to study it and play with it a little.  While it is a most ingenious way of showing the hydrogen bond connections, I find it awkward to use the models for instructional purposes.  I seriously doubt that these modifications will be of sufficient usefulness to the average student to warrant the extra expense and complication.  Another limitation is the fact that the two wires which keep the double strand together fix the model in such a way that single nucleotide units cannot be put in or taken out.
I'd like to tell you again how popular and valuable the models were in our general biochemistry course.  We distributed four nucleotide pairs gratis and invited those who wished to build a large-scale model to buy their own.  On this basis, we sold fifty or more models to a class of about one hundred.
With warmest regards,
Sincerely yours,
Arthur Kornberg