^Karin Friedrich, The Other Prussia: Royal Prussia, Poland and Liberty, 1569-1772, p. 150, 2006 [1] Frederick William gained the East Pomeranian districts of Lauenburg and Bütow (Lębork and Bytow), which had returned to Polish rule as fiefs after the ...
^J. H. W. Verzijl, W. P. Heere, J. P. S. Offerhaus, International law in historical perspective[cần số trang]
^Beth Lettow Brusius, John Milton Liittschwager, The Lettows, B.L. Brusius, 1984, p.14 however, this excluded the lands of Lauenburg and Butow which reverted to Poland