Steven; White Smith, Gregory. Van Gogh: The Life. Profile Books. 2011: 822 ff. ISBN 978-1-84668-010-6. Hulsker (1980) p. 476 van der Veen and Knapp (2010)
Raddi ex Steud., 1840 Eutacta compacta Carrière Michael Knapp, Ragini Mudaliar, David Havell, Steven J. Wagstaff & Peter J. Lockhart. The drowning of New
Alexis Knapp Gives Birth to Baby Girl. Us Weekly. 2011-07-07 [2011-07-07]. (原始内容存档于2011-07-08). Ryan Phillippe's Last Name Given to Alexis Knapp's Baby