@book{BrykRaudenbush2002,
  title     = {Hierarchical linear models: {A}pplications and data analysis methods},
  author    = {Raudenbush, Stephen W and Bryk, Anthony S},
  volume    = {1},
  year      = {2002},
  publisher = {Sage}
}


@book{Hedeker2006,
  author    = {Hedeker, D. R. and Gibbons, R. D.},
  title     = {Longitudinal data analysis},
  year      = {2006},
  address   = {Hoboken},
  publisher = {John Wiley}
}