27 Moreover, in the twelfth century, a writer of the highest repute, among the Armenians, clearly expounded his views of this matter in these words: 'We speak of Christ as one nature, not to imply confusion as does Eutyches, nor diminution, as does Apollinaris, but in the sense of Cyril of Alexandria, who in his book Scholiorum Adversus Nestorium says, "There is one nature of the Incarnate Word as the Fathers taught". And we also teach this according to the tradition of the saints, but not according to the opinion of heretics. For they introduce confusion and change and alterations into the union in Christ. We say there is one nature referring to the hypostasis, which you also speak of in Christ; and this is correct and granted by us, and equally valid is our own expression: "One Nature." Nor do we refuse to say "two Natures", provided there is no implication of the division maintained by Nestorius, but the expression is used against the confusion introduced by Eutyches and Apollinaris' (Nerses iv, 1173) in his Libellum Confessionis Fidei to the Emperor Manuel Comnenus (cf. I. Capelletti S. Narsetis Claiensis Armenorum Catholici, Opera. I, Venice 1836, pp. 182-83).
Source: Sempiternus Rex Christus (Vatican.va)