/usr/share/doc/python-ufl/demo/NonlinearPoisson.ufl is in python-ufl-doc 2017.2.0.0-2.
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1 2 3 4 5 6 7 8 9 10 11 | # nonlinear_poisson.ufl
element = FiniteElement("Lagrange", triangle, 1)
v = TestFunction(element)
u = TrialFunction(element)
u0 = Coefficient(element)
f = Coefficient(element)
a = (1+u0**2)*dot(grad(v), grad(u))*dx \
+ 2*u0*u*dot(grad(v), grad(u0))*dx
L = v*f*dx - (1+u0**2)*dot(grad(v), grad(u0))*dx
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