Complex sentence: However in the authoritative and encyclopaedic "Biographical Dictionary of British Architects 1600-1840" (4th Edn; 2008) by Sir Howard Colvin she is mentioned only once, as a patroness.
Split into simpler sentences: However in the authoritative and encyclopaedic Biographical Dictionary of British Architects 1600-1840 4th. Ed.2008 by Sir Howard Colvin she is mentioned once-as a patroness.