AC magnetic susceptibility studies of Ag-sheathed Y1-xCaxBa2Cu3O7-δ tapes (x = 0 and 0.3) - Nazarova, E.; Buchkov, K.; Zahariev, A.; Georgiev, J.; Nenkov, K.; Ignatov, H.; Kovachev, V.; Burzo, E.; Balasz, I.