It was shown that small lead particles of a size of 1 ~tm and smaller distributed in a copper matrix can cause this heterogeneous alloy to exhibit complete superconductivity. According to the size of the lead particles and their distribution the transition temperatures vary between 0,3 and 7 ~

We have discovered the superconductivity of sodium tungsten bronzes. The transition temperatures are in the range below 1°K.It was Hagg 1 and his collaborators who first explained the nature of these crystals. The formula is Na WO" with 0.1

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