+ "<div class=\"graph-button\" onClick=\"zoom_reference ('"+id+"');\">!</div>"
+ "</div>"
+ "<div class=\"graph-buttons navigation\">"
- + "<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>"
+ "<div class=\"graph-button\" onClick=\"zoom_in ('"+id+"');\">+</div>"
- + "<div class=\"graph-button\" onClick=\"zoom_later ('"+id+"');\">→</div>"
+ + "<div class=\"graph-button\" onClick=\"zoom_later ('"+id+"');\">\u2192</div>"
+ "</div>"
);
});