Ah, fond memories. I recall a bus ride through snowed in Denver in 1984, to get a copy of the original blue box article referenced in phone phreak lore at the downtown library, just to find that these pages had long been removed from the journal copy.

Here the article I believe in question: "Pushbutton Calling with a Two-Group Voice-Frequency Code, Schenker, L.", http://bstj.bell-labs.com/oldfiles/year.1960/BSTJ.1960.3901.....

There is an older article covering dial tones (DTMF): "In-Band Single-Frequency Signaling, Weaver, A.; Newell, N.A.", found in http://bstj.bell-labs.com/oldfiles/year.1954/BSTJ.1954.3306....