The favard class for a parabolic problem with wentzell boundary conditions

We consider the operator (Formula presented.) with domain (Formula presented.), where the conditions 4u(j)=0(y=0,1) are called Wentzell boundary conditions. Under suitable assumptions on øan explicit description of the Favard class of A is given An explicit nontrivial example of such an operator A is given at the end of the paper. © 2001, Taylor & Francis Group, LLC