8 books • 5 series
Four-Color Problem (Pure and Applied Mathematics, #27)
Graphs and Their Uses (New Mathematical Library S.)
Four-colour Problem
Invitation to Number Theory (Anneli Lax New Mathematical Library)
Four-Color Problem, The. Pure and Applied Mathematics
Niels Henrik Abel
Cardano (Princeton Legacy Library, #4972)
Number Theory and Its History (Dover Books on Mathematics)