Sato, H. and Tomimatsu, A. (1973) Gravitational Field of Slowly Rotating Deformed Masses. Progress of Theoretical Physics, 49, 790-799.
http://ptp.oxfordjournals.org/content/49/3/790.full.pdf

has been cited by the following article:

• TITLE: Approximate Metric for a Rotating Deformed Mass

  AUTHORS: Francisco Frutos-Alfaro, Paulo Montero-Camacho, Miguel Araya, Javier Bonatti-González

  KEYWORDS: Approximate Solutions of Einstein Equations, Kerr Metric, Erez-Rosen Metric, Quadrupole

  JOURNAL NAME: International Journal of Astronomy and Astrophysics, Vol.5 No.1, March 4, 2015

  ABSTRACT: A new Kerr-like metric with quadrupole moment is obtained by means of perturbing the Kerr spacetime. The form of this new metric is simple as the Kerr metric. By comparison with the exterior Hartle-Thorne metric, it is shown that it could be matched to an interior solution. This approximate metric may represent the spacetime of a real astrophysical object with any Kerr rotation parameter a and slightly deformed.