The four color problem:
Saaty, Thomas L.
The four color problem: assaults and conquest. Thomas L. Saaty - New York: Dover Publications, 1986. - v, 217p.
The four color problem.
519.17 / SAA
The four color problem: assaults and conquest. Thomas L. Saaty - New York: Dover Publications, 1986. - v, 217p.
The four color problem.
519.17 / SAA