A General Class of Estimators of Population Median Using Two Auxiliary   Variables in Double Sampling
  In this paper we have suggested two classes of estimators for population median M_Y of the study character Y using information on two auxiliary characters X and Z in double sampling. It has been shown that the suggested classes of estimators are more efficient than the one suggested by Singh et al (2001). Estimators based on estimated optimum values have been also considered with their properties. The optimum values of the first phase and second phase sample sizes are also obtained for the fixed cost of survey. 
Jack Allen, Housila P. Singh, Sarjinder Singh, Florentin Smarandache