.attr("transform", "translate(" + BwDrawer.margin.left + "," + BwDrawer.margin.top + ")");
 
   var form = d3.select(selector).append("form")
+      .attr("class", "graph-period")
       .attr("action", "#");
   BwDrawer.periods.forEach(function(p) {
     var div = form.append("div");
 
   });
 
   var form_source = d3.select(drawer.selector).append("form")
+      .attr("id", "weight-sources")
       .attr("action", "#");
   WeightsDrawer.sources.forEach(function(s) {
     var div = form_source.append("div");
       .attr("transform", "translate(" + WeightsDrawer.margin.left + "," + WeightsDrawer.margin.top + ")");
 
   var form_period = d3.select(drawer.selector).append("form")
+      .attr("class", "graph-period")
       .attr("action", "#");
   WeightsDrawer.periods.forEach(function(p) {
     var div = form_period.append("div");