2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/33797Clairin's method of obtaining Bäcklund transformations is applied to Einstein's field equations for the interior of a uniformly rotating stationary axisymmetric perfect fluid. It is shown that for arbitrary pressure $p$ and mass density $μ$ the method does not give non-trivial Bäcklund transformations, while if $μ+ 3p =0$ it gives the transformation of Ehlers.General Relativity and Quantum Cosmologytext