**Volume 8** ▶ Number 1 ▷ Number 2 ▷ Number 3 ▷ Number 4

**Restrictive factor: Definition, properties and problems**

*Original research paper. Pages 117—119*

Krassimir T. Atanassov

Full paper (PDF, 82 Kb)

**A note on the elementary number theory**

*Original research paper. Pages 120—124*

Krassimir T. Atanassov

Full paper (PDF, 140 Kb)

**On a way for introducing metrics in Cartesian product of metric spaces**

*Original research paper. Pages 125—128*

Peter M. Vassilev and Mladen V. Vassilev-Missana

Full paper (PDF, 139 Kb)

**On one remarkable identity related to function π(x)**

*Original research paper. Pages 129—136*

Mladen V. Vassilev-Missana

Full paper (PDF, 239 Kb)

**A note on solving and analysing of the full cubic equation**

*Original research paper. Pages 137—144*

Blagoi N. Djokov

Full paper (PDF, 282 Kb)

**Intervals containing prime numbers**

*Original research paper. Pages 145—148*

Laurențiu Panaitopol

Full paper (PDF, 128 Kb) | Abstract

*x*> 0, let π(

*x*) be the number of prime numbers not exceeding

*x*. One shows that, for

*x*> 7, there exists at least one prime number between

*x*and

*x*+ π(

*x*), thus obtaining a result that is sharper than the one postulated by Bertrand.