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          | Abstract: |  
          | We are going to analyze the traveling waves problem of
 $$
 u_t= (a(u, u_x) )_x+f(u),\qquad (t,x)\in \mathbb{R}^2,
 $$
where  $a(u, u_x)$ is an increasing function in the second component and
$f$ is of Fisher type. 
The main problem is to make sense of the singular solution to
provide information on the speed of propagation of the evolution of a compact supported initial data. |  |