I. Socha (red.), "Z dziejów książek, bibliotek i czytelnictwa na Śląsku" (S. -114). Katowice : Wydawnictwo Uniwersytetu Śląskiego
Studia Bibliologiczne;t. 11
There are many references regarding the circulation of correspondence in archival documents. Radziwills employed special „postmen” and messengers, most often Tatars which were paid for delivering a definite parcel. Letters were sent by the reliable messengers who sometimes completed information verbally, copies of letters directed to different places were prepared. The principle of secrecy of correspondence was obeyed, although the magnates authorised some secretaries and courties to open the letters addressed to them, select and formulate answers. Sending the correspondence in war times caused many difficulties due to robberies, taking over the letters by an enemy etc.