format
A list providing a summary of the data. The list contains:
lcl{
sur$means : the mean vector,
sur$stddev : the vector of standard deviations,
sur$corr : the correlation matrix, and
sur$n : the sample size.
}source
Drton, M. & Richardson, T.S. (2004) Multimodality of the likelihood
in the bivariate seemingly unrelated regressions
model. Biometrika 91(2): 383-392.