Paper/Outline of a Mathematical Theory of Computation

Scott, Dana (January 1, 1970). "Outline of a Mathematical Theory of Computation". local page: Oxford University Computing Laboratory Programming Research Group. 

As one read this seminal paper/book, it should be noted that this idea is profoundly simple. To help better perceive this simplicity, Tai-Danae Bradley has a blog entry The Most Obvious Secret in Mathematics on this matter.

An important note

I manually transcribed the whole document into Google Doc. In theory, this can also be automatically converted to any other document format using Pandoc. An important point about this document is in its title. If we were to replace the term, Computation to Decision, this paper would have immediately mean a lot more to mere mortals without any loss of its correctness.