function Alok = alok_gradgrad(uzly_lok,tau_lok)

R_lok = [ uzly_lok(:,2)-uzly_lok(:,1) , uzly_lok(:,3)-uzly_lok(:,1) ];

B = inv(R_lok)' * [ [-1;-1] [1;0] [0;1] ];

Alok = tau_lok * B' * B * abs(det(R_lok)) / 2;
