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.

### Number 7

#### Publication Date: 1969

On The Abstract Quasi-linear Differential Equation

Michiaki WATANABE; 1-16

Note On Positive Linear Maps Of Banach Algebras With An Involution

Seiji WATANABE; 17-21

On 3-dimensional Riemannian Manifolds Satisfying A Certain Condition On The Curvature Tensor

Kouei SEKIGAWA and Hitoshi TAKAGI; 23-27

On 4-dimensional Connected Einstein Spaces Satisfying The Condition $R(X, V)\cdot R=0$

Kouei SEKIGAWA; 29-31