Zeileis A, Croissant Y (2010). “Extended Model Formulas in R: Multiple Parts and Multiple Responses.” Journal of Statistical Software, 34(1), 1–13. doi:10.18637/jss.v034.i01.
@Article{,
title = {Extended Model Formulas in {R}: Multiple Parts and Multiple Responses},
author = {Achim Zeileis and Yves Croissant},
journal = {Journal of Statistical Software},
year = {2010},
volume = {34},
number = {1},
pages = {1--13},
doi = {10.18637/jss.v034.i01},
}