Lopotko, O. V. “Representations of the Additive Group of a Nuclear Space in Terms of Self-Adjoint Operators”.
Ukrains’kyi Matematychnyi Zhurnal
, vol. 51, no. 2, Feb. 1999, pp. 271–274,
https://umj.imath.kiev.ua/index.php/umj/article/view/4609
.