Links for 2D diffusion (Diffusive Initial Value Problem)

Numerical Recipes

19.2 Diffusive Initial Value Problems 847 (PDF)

19.3 Initial Value Problems in Multidimensions 853 (PDF)

PDE Categorization, Boundary Conditions and Numerical Solutions
14.3 Parabolic (diffusive) initial value problems
--- this is almost same as the Numerical Recipes book.

8. Partial differential equations

Algorithm (Crank-Nicolson; or Crank-Nicholson)

solving diffusion equation numerically (Japansese)