Who created the Kirkpatrick numbering system for Domenico Scarlatti’s sonatas?

The Kirkpatrick numbering system for the sonatas of Domenico Scarlatti was created by the American musicologist and harpsichordist Ralph Kirkpatrick in the 1950s.12

Kirkpatrick established this system in his 1953 monograph, Domenico Scarlatti, where he provided a complete list of the 555 sonatas organized in chronological order based on their manuscript and printed collections. In this system, each work is designated by a number preceded by the letter "K". This numbering replaced the earlier system developed by Alessandro Longo and is now the standard method for identifying Scarlatti's keyboard works.31