The Big Book of Logic Puzzles - Mathrax 400 Hard (Volume 57) in Bloomington, MN

Mathrax consists of a square grid. The goal is to fill in each cell with numbers from 1 to N, where N is the size of the puzzle's side. No number may appear twice in any row or column. Circles with additional conditions may be situated on intersections of lines inside the grid.A number and a sign of mathematical operation (addition, subtraction, multiplication, division) - a number is a result of an operation execution with numbers in diagonally adjacent cells.A letter "E" ("even") - all numbers in four cells are even.A letter "O" ("odd") - all numbers in four cells are odd.