Incorrect method for calculation of grey water footprint in several articles

The aim of research is to acquire new knowledge, discover new practices and methods, or simply improve existing ones. Sometimes these are dead ends, and the chosen direction of research is incorrect. This can even happen when the underlying assumptions may sound logical. Fu et al. use the incorrect method for the calculation of grey water foot-print in their article "Measurement and driving factors of grey water footprint efficiency in Yangtze River Basin ". Therefore, the results are biased. The results of greywater footprint for industry and households are underestimated, which emphasizes the contribution of agriculture to the total water footprint. In this Letter to Editors, numerical proof is provided that the used equation is incorrect. Unfortunately, there are three other articles which use the same incorrect equation. Two of these articles were published in the journal Science of the Total Environment. The edi-tors are asked to initialize a correction process of these articles because a transparent corrections process is essential to assist in the maintenance of public confidence in research.