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 17

#### Publication Date: 1980

On The Compact Connected Transformation Group Of N-sphere With Codimension Two Principal Orbit

Haruo KOMIYAMA and Tsuyoshi WATABE; 1-21

On The $\ell$ -class Field Towers Of Cyclic Fields Of Decree $\ell$

Teruo TAKEUCHI; 23-25

A Note On The Cut Loci And The First Conjugate Loci Of Riemannian Manifolds

Ryō TAKAHASHI; 27-31

On Energy Inequalities For The Mixed Problems For The Wave Equation In A Domain With A Corner

Kazuo ASANO; 33-38

On A Type I Factor Direct Summand Of A $W^{*}$ -tensor Product