Investigating Factors Affecting on Per Capita GDP Growth in Different Groups of Countries with Emphasis on Governance Indicators
                        
                        
                        
                        
                        Estimating Price and Production Elasticities of Natural Gas in the Manufacture of Basic Metals Industries of Iran
                        
                        
                        
                        
                        Comparative Analysis of Kuznets Hypothesis in Selected Developing Countries (Emphasis on Development Indicators)