Israeli mecenaries in 1977 Ethiopia

I was reading some article at strategypage.com when this caught my attention :

“In 1977, Israeli mercenaries achieved at least seven kills flying Ethiopian F-5As against Somali MiG-21s. “

The article can be found at : http://www.strategypage.com//fyeo/howtomakewar/default.asp?target=HTAIRFO.HTM

Aside from http://www.acig.org/artman/publish/article_192.shtml
what other source can describe this in detail.