Black Holes : Theory and ObservationFriedrich W Hehl, Claus Kiefer, Ralph J.K. Metzler · First published 2013Open the Tome
Gauge Theories Of Gravitation A Reader With CommentariesFriedrich W. Hehl · First published 2012Open the Tome
ReduceFriedrich W. Hehl, Volker Winkelmann, Hartmut Meyer, Friedrich W Hehl · First published 1993Open the Tome
