m4 Powerful (Turing-equivalent) implementation of traditional Unix macro-expansion program, designed as preprocessor to more stubborn languages. Ugly, but fairly standard, available on most platforms. http://www.gnu.org/software/m4/m4.html

GNU m4 - Development site René Seindal's site for developing the Free Software Foundation's version of the Unix macro processor. http://www.seindal.dk/rene/gnu/

Eli specification of ALGOL 60 from which an analyzer for ALGOL 60 can be generated. http://citeseer.ist.psu.edu/396935.html