S. M. Bisong
College of Technology, University of Buea; Department of Mechanical Engineering, ENSET Douala, University of Douala
Cameroon

Samuel Mbelle Bisong

P. O. Box 63, Buea

P.O. Box 1872, Douala

V. V. Lepov
Larionov Institute of Physical-Technical Problems of the North of Siberian Branch of the Russian academy of sciences, — Separate Division of Federal research Center «Yakut Scientific Centre SB RAS»
Cameroon

Valeriy V. Lepov

1, Oktyabrskaya, Yakutsk, 677007

A. R. Etinge
Department of Civil Engineering, ENSET Douala, University of Douala
Cameroon

Ambalo Renel Etinge

P.O. Box 1872, Douala