private void manageMinMaxCluster(final StringBuilder sb) {
		final List<String> minPointCluster = new ArrayList<String>();
		final List<String> maxPointCluster = new ArrayList<String>();
		for (Cluster cluster : bibliotekon.allCluster()) {
			final String minPoint = cluster.getMinPoint();
			if (minPoint != null) {
				minPointCluster.add(minPoint);
			}
			final String maxPoint = cluster.getMaxPoint();
			if (maxPoint != null) {
				maxPointCluster.add(maxPoint);
			}
		}
		if (minPointCluster.size() > 0) {
			sb.append("{rank=min;");
			for (String s : minPointCluster) {
				sb.append(s);
				sb.append(" [shape=point,width=.01,label=\"\"]");
				sb.append(";");
			}
			sb.append("}");
			SvekUtils.println(sb);
		}
		if (maxPointCluster.size() > 0) {
			sb.append("{rank=max;");
			for (String s : maxPointCluster) {
				sb.append(s);
				sb.append(" [shape=point,width=.01,label=\"\"]");
				sb.append(";");
			}
			sb.append("}");
			SvekUtils.println(sb);
		}
	}