parens - Robuta Search

https://within-parens.blogspot.com/2009/

Marco Antoniotti's blog on Lisp and other interesting bits of programming.

https://www.boost.org/doc/libs/1_80_0/libs/vmd/doc/html/header/boost/vmd/is_parens_empty_hpp.html

https://tug.org/pipermail/xetex/2007-November/007827.html