1.

The World Factbook 2008 Central Intelligence Agency

The World Factbook 2008 מאת Central Intelligence Agency

2.

Zaire: A Country Study (Area Handbook Series) Sandra W. Meditz

Zaire: A Country Study (Area Handbook Series) מאת Sandra W. Meditz

3.

NIOSH Pocket Guide To Chemical Hazards Claitors (DST)

NIOSH Pocket Guide To Chemical Hazards מאת Claitors (DST)