Letters to the Editor.

Presents several letters to the editor referencing articles that were published in the previous issues of the journal "Communications of the ACM." "Implementing Phrase-Structure Productions in PL/I," which focused on a PL/I program for-randomly generating terminal strings of a BNF language; Computation that was done in FORTRAN on CDC 6400 in single precision; "On Compiling Algorithms for Arithmetic Expressions,"which focused on an algorithm on the compilation of arithmetic expressions; Objections to the choice of Ljubljana, Yugoslavia as the site for International Federation for Information Processing Congress 1971.