Perkins, J. David (1999). "The gunner and the U-boat". The World War I Document archive: The War at Sea. Great War Primary Documents Archive. Retrieved 6 March 2009. See additional note no. 2.
Both of the Perkins works report the date of the encounter as Sunday, 16 August 1915, but 16 August 1915 was actually a Monday. Messimer (p. 129), Gibson and Prendergast (pp. 50–51), and Uboat.net (Helgason, Guðmundur. "WWI U-boats: UB 4". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net.) all report the date of the encounter as 15 August 1915.
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Helgason, Guðmundur. "Ships hit during WWI: Laurestina". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 6 March 2009.,
Helgason, Guðmundur. "Ships hit during WWI: Quivive". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 6 March 2009.,
Helgason, Guðmundur. "Ships hit during WWI: Welfare". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 6 March 2009.,
Helgason, Guðmundur. "Ships hit during WWI: Intrepid". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 6 March 2009.
Helgason, Guðmundur. "Ships hit during WWI: Bona Fide". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 5 March 2009.
Helgason, Guðmundur. "Ships hit by UB 2". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net., Helgason, Guðmundur. "WWI U-boats: UB 16". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 6 March 2009.