The Theory of Concatenative Combinators (2007)

I'm a big fan of combinatory logic, as it's simpler than lambda calculus and avoids the trickiness of contexts/environments (personally, I don't see why people keep avoiding de Bruijn indices...).

I made a bit of an experiment with concatenative combinators at http://chriswarbo.net/blog/2012-05-13-concatenative_language...

Other interesting branches are illative combinatory logic and binary combinatory logic.

I'm still waiting for an excuse to use Joy or one of its descendents for a substantial project!

I recommend adding (2007) to the title.