• Sensitivity of ZnO films doped with Er, Ta and Co to NH3 at room temperatureDimova-Malinovska, D.; Nichev, H.; Georgieva, V.; Angelov, O.; Pivin, J.-C.; Mikli, ValdekPhysica status solidi (a) : applications and materials science2008 / 8, p. 1993-1997 : ill https://link.springer.com/chapter/10.1007/978-1-4020-9916-8_32