SEDfit: Software for Spectral Energy Distribution Fitting of Photometric
  Data
  This paper describes SEDfit, the earliest --- but continually upgraded ---
software package for spectral energy distribution fitting (SED fitting) of
high-redshift photometric data, and the only one to properly treat
non-detections. The principles of maximum-likelihood SED fitting are described,
including formulae used for fitting both detected and un-detected (upper
limits) photometric data. The internal mechanics of the SEDfit package are
presented and several illustrative examples of its use are given. The paper
concludes with a discussion of several issues and caveats applicable to
SED-fitting in general.
