The ferry service between the Bulgarian harbours Vidin and Silistra according to an American CIA report dated 7 April 1954

An item reported that between the Bulgarian towns Vidin and Silistra the steamships Dimitrov and Vasil Kolarov were used for maintaining a regular ferry line with as travel time 20 hours. Underway was stopped at Lom, Oryakhovo, Somovit, Swishtov, Ruse and Tutrakan. The Dimitrov with as approximated dimensions 100 x 20-25 metres was able to take 700-800 passengers with her. The other ship was of smaller dimensions.

Source
The report was published on www.archive.org, document number CIA-RPD80-00810A000500340010-8.