% Session p. 208

f = inline('poisson([0,0],[10,1],0,[1,1,0,0],sol,h)','sol','h');
order = 2; tol = 1e-11; nmin = 4;
[p,err,ampl] = richardson(tol,order,nmin,f,'Cholesky');
p, err = max(err,ampl*3.9e-13)