The following is an extensive survey of world citizenship laws which was produced by Office of Personnel Management of the US government in 2000/2001.
The directory provides information on the the citizenship laws for some 206 countries. It discusses multiple citizenship and the many different diverse countries consider the right of citizenship. Each countries citizenship laws are are summarized.
Understand that this is not a detailed legal analysis. IYou can use it as a qucik refrence but if you truly need to find out about the citizenship laws of a particular country it would be best to begin with it's consulate or with a practicing attorney.
Citizenship laws are in constant flux, so some of the information may be obsolete.
SAO TOME AND PRINCIPE
ST. KITTS AND NEVIS
ST. VINCENT AND THE GRENADINES