See also the Extended u'g'r'i'z' Standard Star Network
The u'g'r'i'z' Standard Star Network has been published in the April 2002 issue of the Astronomical Journal (Smith et al. 2002, AJ, 123, 2121). Machine readable tables of their u'g'r'i'z' magnitudes and colors and of their astrometric and spectral properties are available from the electronic edition.
The u'g'r'i'z' standard stars and their calibrated magnitudes and colors can be found tabulated at this URL. Their astrometric and spectral properties can be found tabulated at this URL.
Results for the search for any global trends in the u'g'r'i'z' system can be found at this URL.
The transmission curves of the USNO40 u'g'r'i'z' filters and the response functions of the USNO40 telescope + CCD + u'g'r'i'z' filters can be found at this URL.
A southern extension to the u'g'r'i'z' system is being developed on the CTIO 36-in and a Tek2048, an instrument setup very similar to that of the USNO40. See this URL for more information.