I have located the late Vladigerov pieces from Edition Elm--With these dates, they are most assuredly under copyright and available for about 20 Euros EACH. I guess this puts an end to the possibility of Vol.6
Three Short Pieces for piano op. 64 (1972)
Four Pieces for piano op. 65 (1973)
Five Silhouettes for piano op. 66 (1974)
Five Poetic Pictures for piano op. 68 (1976)
Four Fresques for piano op. 69 (1977)
Three Bagatelles for piano op. 70 (1978)
Towards the end of his life, Vladigerov made a number of two piano arrangements of some of his earlier works, also available from Elm
Valse fantastique op. 2, No. 4, for two pianos
Swedish Dance op. 13, No. 2, for two pianos
Romanian Dance op. 38, No. 3, for two pianos,
Hora staccato w/o opus, for two pianos
Rhapsody Vardar op. 16, for two pianos
Mar Dimitro lyo – Bulgarian dance op. 23, No. 2, for two pianos
Bilyana – Bulgarian dance op. 23, No. 6, for two pianos
Grande ronde – Bulgarian dance op. 23, No. 7, for two pianos
Bulgarian Suite op. 21, for two pianos
La danseuse Orientale op. 10, No. 2, for two pianos
Shimmy de concert w/o opus, for two pianos
Romance and Cakewalk w/o opus, for two pianos
Vladigueroff – Foxtrot w/o opus, for two pianos
Link:
http://www.editionelm.eu/cpv_e.htm#702