iii
Acknowledgement
We are delighted to express our thanks to the carter center for
the financial, material and moral support with out which this
material wouldn’t come to reality.
We are also glad to extend our heart felt appreciation for Ato
Esayas Alemayehu, Ato Muluken Eyayu, Ato Wossen Tafere
and Ato Dagnew Engidaw for their critical and constructive
comments that are found to be highly essential for this lecture
note preparation.
We are very happy to be members of the faculty of health
sciences, Alemaya university for the fact that working with
such faculty are really incomparable.