Oxford Reference [Sources] - collection of scholarly online reference sources. Select "performing arts" as a subcategory.
Grove Music Online - music is intimately related to dance and performance. The Grove music is an excellent ancillary source for dance-topic issues.
Biography Index - Contains more than one million thumbnail biographies from scholarly sources.
Biography and Geneology Master Index - Indexes readily-available biographical reference sources, people from all places, times and occupations. NO DIRECT INFO HERE (a 2-step source to hard-copy sources).
Grove Encyclopedia of Music - scholarly encyclopedia of music and musicians. Includes world music and dances