1945 SARAJEVO, complete set in block of four

Only four sets in block of four have been noted so far. Only this one was seen in last few decades, so looks like it is the only one that remained.

1945 Sarajevo local provisional issue, complete set in block of four. Certificate Ercegović and Veličković.

 Update:  Thanks to Mr. Vilfan, I found out where other three sets should be or at least where they formerly were. One of them is 100% confirmed because I saw its scan.