author = { Sonneck, Oscar George Theodore Library of Congress },

title = { Catalogue of opera librettos printed before 1800 prep. by Oscar George Theodore Sonneck. Library of Congress },

publisher = {Government Printing Office},

year = {19XX-},

abstract = {Katalog <Washington, DC, Library of Congress>},

address = { Washington, DC },

url = { http://slubdd.de/katalog?TN_libero_mab2 }