@article {Риков1981,
	title = {Основа и флексия в индоевропейската и праславянската глаголна система},
	journal = {Съпоставително езикознание / Сопоставительное языкознание / Contrastive linguistics},
	volume = {6},
	year = {1981},
	pages = {14{\textendash}18},
	abstract = {Due to the appearance of the new imperfective formation *-{\v e}ax- in Proto-Slavonic, the verb system became the basic medium for expressing temporal relations. That is why the old opposition between primary and secondary inflexions became redundant, the result being a partial neutralization of that opposition; cf. the Old Bulgarian inflexions for the third person singular, the first, second and third person plural and the dual.},
	author = {Риков, Георги}
}
