1. S.L. Wiegand, US Patent 155602 (1874).
2. W.S. Holdaway, US Patent 1218602 (1915).
3. Societe Anonyme des Establish A. Oiler, British Patent 180638 (1922).
4. C.O.J. Montelius, US Patent 1698802 (1925).
5. P. Leistritz, F. Burghauser, German Patent 453727 (1927).