\bibstyle{alpha} \citation{Ash} \citation{Delgado:1998} \citation{commutative} \citation{Ash} \citation{Delgado:1998} \citation{commutative} \citation{Delgado&Fernandes:2000} \citation{Almeida:book}
\bibstyle{alpha} \citation{Ash} \citation{Delgado:1998} \citation{commutative} \citation{Ash} \citation{Delgado:1998} \citation{commutative} \citation{Delgado&Fernandes:2000} \citation{Almeida:book}