orrected) zenith
%     angles in decimal degrees. If SunZen is a vector it must be of the
%     same size as all other vector inputs. SunZen must be >=0 and <=180.
%
%% Outputs
%%
% * *|SkyDiffuse|* - the diffuse component of the solar radiation  on an
%     arbitrarily tilted surface as given by a model developed by David L.
%     King at Sandia National Laboratories (retired). 
%
%% Example
%
SurfTilt = 30;
SurfAz = 180;
DHI = 47;
GHI = 473;
SunZen = 60;
SkyDiffuse = pvl_kingdiffuse(SurfT