Before revision:  As a practical illustration, we test the Environmental Kuznets Curve (EKC) hypothesis for six early industrialized countries . The more efficient and more powerful FMGLS approach raises important questions concerning the standard model specification for EKC analysis .
After revision:  As a practical illustration, we test the Environmental Kuznets Curve (EKC) hypothesis for six early industrialized countries as in Wagner et al. (2020) .