D.S. Yasyrkina, S.V. Kuznetsov, A.V. Ryabova, D.V. Pominova, V.V. Voronov, R.P. Ermakov, P.P. Fedorov. Dependence of quantum yield of up-conversion luminescence on the composition of fluorite-type solid solution NaY1-x-yYbxEryF4. // Nanosystems: physics, chemistry, mathematics. 2013. 4(5). P.648-656.