A quadratic curvature Lagrangian of Paw{\l}owski and R\c{a}czka: a finger exercise with MathTensor

Recently Paw{\l}owski and R\c{a}czka proposed a unified model for the fundamental interactions which does not contain a physical Higgs field. The gravitational field equation of their model is rederived under heavy use of the computer algebra system Mathematica and its package MathTensor.