The Sale and Purchase of Landed Estates in the Region of Łęczyca at the End of the Fourteenth Century and at the Beginning of the Fifteenth Century - Morawski, Zbigniew (. Quaestiones medii aevi novae. - Warszawa : Fundacja Centrum Badán Historycznych, 1996-. - ISSN 1427-4418 6, 2001)