Writing.
I've sold a couple of articles, too, on endurance and mountaineering. Shorter, and of the "helpful tips" variety.
It was very clear that the rights to one of those articles remained mine, the magazine that purchased it bought the rights to print it first and that was it.
The other was the property of the magazine, in perpetuity and for whatever purpose they chose.
I was hoping they'd make a billion off of it. Something would have trickled down.
Nothing did happen with either of 'em. I suspect I'm more published than read. And I'm not much published.
Arf