#3398-3401 Bulgaria - World Wildlife Fund: Bats, Set of 4 (MNH)
1989 World Wildlife Fund (WWF): Bats, Set of 4 stamps. Designs: 5s, Nyctalus noctula (The common noctule). 13s, Rhinolophus ferrumequinum (Greater horseshoe bat). 30s, Myotis myotis (Greater mouse-eared bat). 42s, Vespertilio murinus (parti-colored bat).