docs: function handleResolution(options, ws, resIdx, config, progress, callback) {
  
    // Resolution object
    let res = options.tiles.resolutions[resIdx];
  
    // Workspace of this resolutions
    let resWs;
  
    if (options.tiles.resolutions.length == 1) {
      resWs = ws;
    } else {
      resWs = ws + '/' + res.id;
    }
  
    // Create directory of resolution workspace
    fs.ensureDir(resWs, (err) => {
      // Error
      if (err) {
        // Directory could not be created.
  
        // Call callback function with error.
        callback(err);
      } else {
        // No errors
  
        // Handle all wms
        handleWMS(options, resWs, res, 0, config, progress, (err) => {
  
          // Error
          if (err) {
            // It could not be handled all wms.
  
            // Call callback function with error.
            callback(err);
          } else {
            // No errors
  
            // Raise resolution index
            resIdx++;
  
            // New resolution index exists
            if (resIdx < options.tiles.resolutions.length) {
              handleResolution(options, ws, resIdx, config, progress, callback);
            } else {
              // New resolution index does not exists
  
              // Call callback function without errors. All resolution
              // were
              // handled.
              callback(null);
            }
          }
  
        });
  
      }
    });
  
  }