Hassanzadeh Azami, R., Madaah Hosseini, H. R., & Asghari Shivaee, H. "Ultraviolet and Visible Upconversion Emissions in Er3+-Yb3+ Doped Titanium Dioxide Nanopowder under the 980 nm Laser Diode Excitation", Scientia Iranica, 24, 6, 2017, 3500-3504. doi: 10.24200/sci.2017.4424