Programmer's Digest was an unusual vinyl LP magazine targeted for radio broadcast professionals. It was only around briefly, published for just a few years in the early to mid 1970s. Issues were originally sold on a subscription basis, like a print magazine.
There are some true broadcast gems to be found in this series. One of my faves is some great ribbing of recently fallen, but back then on-air, shock-jock Imus at the hands of a gravelly-voiced howler know as the Wolfman Jack.
The LP magazines don't turn up all the time - possibly a small number of subscriptions as compared to the relative expense of pressing up vinyl led to its early demise - and now to its rarity. A few sites offer downloads of snippets from different issues (along with other sources), but to truly get a feel for 1970s radio, its best to spin a platter - analog, baby, analog!