Engineered Systems, Jan. 2017, by Kevin Dickens.
http://www.esmagazine.com/articles/98105-fluid-cooling-in-data-centers-if-not-now-when

"Trends don’t always follow the expected path (or timeline), but the basics remain the basics and increased cabinet density remains inevitable. Let’s revisit the progress of liquid in data center strategy and the tenets of a future-proof(ish) hybrid design for today."