Empirical study on the man-land relationship in Northwest China 并列题名：Empirical study on the man-land relationship in Northwest China Empirical study on the standardization of sentencing of drug crimes in northwest China 并列题名：Empirical study on the standardization of sentencing of drug crimes in northwest China empirical study of the custody and repatriation system Empirical study on teachers' teaching efficacy in northwest rural areas Empirical study on the macro-economic effects of national debt in China Empirical study on the operation mechanism of criminal procedure in China empirical study on the emerging international enterprises empirical study on underdeveloped areas in China