Use this field to specify additional variables across the meta-analysis that identify chromosome position of each marker.This field is used only when one or more of the data sets selected, after the first, uses a variable with another name for the Location Variable. All variable names for the 2nd through the last data set must be specified here.
For example, to specify the additional location variables Position_1 and Position_2, type Position_1 Position_2 in the text box, as shown below: