Moretti and Sorrento refers to a thematic catalogue of the works of Niccolò Paganini. The catalogue was commissioned in 1982 by the city of Genoa in celebration of the bicentenary of Paganini's birth. It was edited by Maria Rosa Moretti and Anna Sorrento, hence the abbreviation "MS" is assigned to Paganini's catalogued works.
References
Moretti and Sorrento Wikipedia(Text) CC BY-SA