I second Adam's recommendation. Most people tend to focus on Bava's horror works, yet this piece is among his strongest. I picked this up in Pittsburgh a few years back because I was tired of seeing other things reference it. If I remember correctly, an Acme skateboards video, the Beastie Boys "Body Movin" video, and Roman Coppola's "CQ" all pay homage to this lovely espionage thriller. And John Phillip Law is amazing!
Props to The Swish for pointing out an erroneously credited Barbarella reference in an early draft of this posting- that was Roger Vadim, not my man Mario B calling the shots. Nice work tracking the influence of this film too, it's just a shame that because Bava broke genres with this (his usual mein being horror) it's not even celebrated by some of his most hardcore fans. I'm at the point where I want to start a petition to get this classic reminted for the DVD generation. Roman Coppola, Beastie Boys- I know you cats are listening (who doesn't pay attention to the crowndozen comment pages?) and it's time to give a little back by using your influence to get this film ressurected.
Word to your moms.