- + "<div class=\"graph-button\" onClick=\"zoom_earlier ('"+id+"');\">←</div>"
- + "<div class=\"graph-button\" onClick=\"zoom_out ('"+id+"');\">−</div>"
+ + "<div class=\"graph-button\" onClick=\"zoom_earlier ('"+id+"');\">\u2190</div>"
+ + "<div class=\"graph-button\" onClick=\"zoom_out ('"+id+"');\">\u2212</div>"