# Internal Forces

with the constant part
${f}^{\mathrm{int}}{}^{0}$
being computed with one-point quadrature and the non constant
part or hourglass part
${f}^{{\mathrm{int}}^{hgr}}$
being computed by perturbation stabilization (`I`_{shell} = 1, 2 ,3 ...) or by physical
stabilization (`I`_{shell} = 22).