There's a dated document that leaked at the start of the decade called The AOL Way that sheds a lot of light on these tactics -

https://www.slideshare.net/cartercole/the-aol-way-leaked-pla...

External links are used for SEO and generally reserved for partner-websites or their own properties to recirculate traffic. Here we have an article reposted from space.com to scientificamerican.com that only links to nature.com and livescience.com. Future US owns space.com + livescience.com, and Springer Nature owns scientificamerican.com + nature.com.