A variational principle for a nonlinear diffusion problem (Q1060925)

Our intention is to construct an extremum variational principle for \[ d^ 2c/dx^ 2-\alpha c/(1+\beta c)=0,\quad dc/dx=0\quad at\quad x=0,\quad c=\gamma \quad at\quad x=L \] on the basis of the results given by \textit{D. S. Djukic} and the author, J. Math. Anal. Appl. 75, 203-218 (1980; Zbl 0429.65083).