function filter_year(){
var objSel = document.getElementById("columns");
objSel.options[1].selected=true;
var obj_Sel = document.getElementById("author");
obj_Sel.options[0].selected=true;
sorter.search('year')
}
function filter_author(){
var objSel = document.getElementById("columns");
objSel.options[2].selected=true;
var obj_Sel = document.getElementById("year");
obj_Sel.options[0].selected=true;
sorter.search('author')
}