[colug-432] Portable Shell

[jep200404 at columbus.rr.com]

Which version of which shell should I write for for excellent portability?
What documentation do you cite for it?

I have used Bourne shell as the standard for portability,
and had though that it had ossified a long time ago,
but was informed that Bourne is under active development,
so now I feel unsettled about Bourne being the standard 
of portability, if it is a moving target. I have not 
found anything about continued development of Bourne 
shell. Bourne quit changing it around 1983.