Abstract Crossword 4x6C19

A mathematics-based, crossword puzzle SYSTEM. Volume 3 of 3. The solutions to the Abstract Crossword puzzles. Introduces the novelty of 2D Regular Expressions! Across and down, simultaneously. Seniors, when you sign up for Medicare coverage of your physical health, at the same time purchase this series of mental exercises to sharpen and re-sharpen your brain on a regular basis.