Reference Question Stumper

I just had a student at the reference desk whose professor is offering extra credit if they can figure out what the significance of the number 39 is in the movie Blow-Up. He said there's a book in the library that will tell them. She had already searched out a dictionary of symbols, and we looked through some others. I also used Reference Universe. When I write out "thirty-nine," it returns several reference articles on the Thirty-Nine Articles of Religion. She read about them in one of our reference books, but doesn't see the connection. I didn't know what else to try, and am not having any luck on the Internet either...

A little while later...
With some tweaking of the search terms in Google, I found the number thirty discussed in a book called After Hitchcock. It's either a reference to Hitchcock's 39 Steps, which has similar themes in its plot, or that Antonioni was living in Europe in 1939. Long live Google Books. Now if they'd only let me print a page or two...