D.V. Pominova, A.V. Ryabova, K.G. Linkov, I.D. Romanishkin, S.V. Kuznetsov, J.A. Rozhnova, V.I. Konov, V.B. Loschenov. Pulsed periodic laser excitation of upconversion luminescence for deep biotissue visualization // Laser. Phys. 26 (2016) 084001. http://dx.doi.org/10.1088/1054-660X/26/8/084001