The names of its rows and columns: the coefficient names of a formula fit, else "(Intercept)", "x1", "x2",
... (aliased coefficients left out).
The covariance matrix (k × k, k the number of coefficients that are not aliased), or the meat with sandwich: false.
R's warnings.
A covariance matrix of the coefficients that are not aliased, with their names: the result of vcovHC and vcovCL.