Young Nicholas John: J-unitary equivalence of positive subspaces of a Krein space. In: Acta scientiarum mathematicarum, (47) 1-2. pp. 107-111. (1984)
Young Nicholas John: A maximum principle for interpolation in H∞. In: Acta scientiarum mathematicarum, (43) 1-2. pp. 147-152. (1981)