Those are official definitions of the Statistics Division of the UN  
(see Glossary at: http://unstats.un.org/unsd/sna1993/glossary.asp?letter=G 
  ):

GDP - expenditure based:
	GDP - expenditure based
Definition 	Expenditure-based GDP is total final expenditures at  
purchasers? prices (including the f.o.b. value of exports of goods and  
services), less the f.o.b. value of imports of goods and services.

Gross national product (GNP):
	Gross national product (GNP)
Definition 	Gross national product (GNP) See ?Gross national income?.
Gross national income (GNI):
	Gross national income (GNI)
Definition 	Gross national income (GNI) is GDP less net taxes on  
production and imports, less compensation of employees and property  
income payable to the rest of the world plus the corresponding items  
receivable from the rest of the world (in other words, GDP less  
primary incomes payable to non-resident units plus primary incomes  
receivable from non-resident units); an alternative approach to  
measuring GNI at market prices is as the aggregate value of the  
balances of gross primary incomes for all sectors; (note that gross  
national income is identical to gross national product (GNP) as  
previously used in national accounts generally).

There are also definitions for:
GDP - income based
GDP - output based
GDP at market prices


Paulo Roberto de Almeida