Variables can be added to the shopping cart by clicking on variables or variable groups in the list on the left hand side of the window. Choose "Add to shopping cart" in the menu that comes up. You can also click the "Add to shoppingcart" button on the variable description page. You can remove variables from the cart by clicking the cross next to the variable information. When the list of variables contains all variables of interest, click the download link for the study in question and attach the resulting file in a letter to the data owner.