Arthur Murray Dance Studios Definition of Bolero.
Ballroom Dancers.com Definition of Bolero.
Latin Sheet Music Definition of the Cuban Bolero.
Music of Puerto Rico Article discussing the differences between the Cuban and Spanish Boleros.
MusicMatch Guide Very good explanatoin of the musical style and history of Bolero.
Salsa and Merengue Definition of Bolero.
Wikipedia Excellent encyclopedic entry on this dance and musical form.