#1931-1935 Czechoslovakia - Hydrological Decade (UNESCO) (MNH)
1974 Hydrological Decade (UNESCO), 1965-1974, Set of 5. Designs: Symbolic Designs: 60h, "Water the Source of Energy." 1k, Importance of water for agriculture. 1.20k, Study of the oceans. 1.60k, "Hydrological Decade." 2k, Struggle for unpolluted water.