docs: private boolean backwardsValidation(int indexSrc, int bestIndex) {
  		double bestScoreV = maxError;
  		int bestIndexV = -1;
  
  		D d_forward = descDst.get(bestIndex);
  		setActiveSource(locationDst.get(bestIndex));
  
  		for( int j = 0; j < locationSrc.size(); j++ ) {
  
  			// compute distance between the two features
  			double distance = computeDistanceToSource(locationSrc.get(j));
  			if( distance > maxDistance )
  				continue;
  
  			D d_v = descSrc.get(j);
  
  			double score = scoreAssociation.score(d_forward,d_v);
  			if( score < bestScoreV ) {
  				bestScoreV = score;
  				bestIndexV = j;
  			}
  		}
  
  		return bestIndexV == indexSrc;
  	}