Harke, B., Ullal, C., Keller, J., & Hell, S. W. (2008). Three-dimensional nanoscopy of colloidal crystals. Nano Letters, 8(5), 1309-1313. Retrieved from http://pubs.acs.org/cgi-bin/article.cgi/nalefd/2008/8/i05/pdf/nl073164n.pdf.