Schaetz, T.; Habs, D.; Podlech, C.; Schramm, U. & Wei, J. Towards crystalline ion beams -- the PALLAS ring trap, report, November 1, 1998; (https://digital.library.unt.edu/ark:/67531/metadc679239/m1/1/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, digital.library.unt.edu; .