NUXALL, T.A. Worcester Ball TW Cask Manual Fill Valves TW-V-*021 and TW-V-*027, report, May 6, 1999; (https://digital.library.unt.edu/ark:/67531/metadc738832/m1/1/: accessed January 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .