private ClusterPair findByClusters(Cluster c1, Cluster c2) {
		ClusterPair result = null;
		for (ClusterPair link : distances) {
			boolean cond1 = link.getLeft().equals(c1)
			        && link.getRight().equals(c2);
			boolean cond2 = link.getLeft().equals(c2)
			        && link.getRight().equals(c1);
			if (cond1 || cond2) {
				result = link;
				break;
			}
		}
		return result;
	}