http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Symmetrical components as applied to the analysis of unbalanced electrical circuits
by C.F. Wagner and R.D. Evans, with an introduction by C.L. Fortescue; used as a text in the design course of the Westinghouse graduate school.