Could anyone enlighten me about the meaning of VN’s  "ray translation"?

As in...
BERETZKY: What is the difference for you between writing in English and writing in Russian? Will you write in Russian again?

NABOKOV: In my prose and poetry during more than half a century of work I have provided enough examples of that difference, whether implicit or creatively expressed, for scholars to analyse. I still use Russian in ray translations (e.g. of LOLITA) and in an occasional poem.

 Nabokov Online Journal (Vol. VIII, 2014)

(I wonder if the intended word is "lay" : an irradiating lapsus when we consider  "Lolita" …