Kevin Matulef Ryan O'Donnell Ronitt Rubinfeld Rocco A. Servedio Testing ±1-weight halfspace. 646-657 2009 APPROX-RANDOM http://dx.doi.org/10.1007/978-3-642-03685-9_48 conf/approx/2009 db/conf/approx/approx2009.html#MatulefORS09