The Nihonkai Mathematical Journal publishes original contributions in all disciplines in mathematics. Between 1964 and 1989, the journal was known as the Science Reports of Niigata University. Series A, Mathematics. Prior to that, Niigata University published mathematical literature as part of the Journal of the Faculty of Science, Niigata University. Series I, Mathematics, Physics and Chemistry.

### Volume 20, Number 2

#### Publication Date: 2009

Bessel potential spaces in Beurling's distributions

Byung Keun Sohn; 73-84

Continuity of a certain invariant of a measure on a CAT(0) space

Tetsu Toyoda; 85-97

Strongly generalized difference $[V^\lambda,\Delta^m,p]-summable sequence spaces defined by a sequence of moduli Ayhan Esi; 99-108 Non-Galois Triple Covering of$\mathbb{P}^2$branched along quintic curves and their cubic equations Hiro-o Tokunaga and Tadasuke Yasumura; 109-126 Common invariant subspaces of two doubly commuting operators on$\ell^2 \otimes \mathbb{C}^2\$

Takahiko Nakazi and Michio Seto; 127-137

A note on the Radon-Nikodym type theorem for operators on self-dual cones

Yasuhide Miura; 139-143

Equivalence classes of mixed invariant subspaces over the bidisk

Kei Ji Izuchi and Masatoshi Naito; 145-154

Instructions to Authors