Ekaterina A. Vlasova. The use of jako recitativum in Russian chronicles of the eleventh-sixteenth centuries
RJANO. 2016. № 2 (32), Pages. 143 - 174

M. Lazar. Evidential Particle de(i) and Other Evidential Particles in the History of Russian
RJANO. 2011. № 2 (22), Pages. 116 - 138