sentence1: 67 through .67d, provide a mechanism for limiting the issues on which a trial-type hearing is required; allow the Postal Service to explain the unavailability of data that would otherwise have to be filed; and provide for data collection for the duration of the experiment.
sentence2: 67 through .67d provide mechanism for limiting issue om which trial-type hearing is required allowing postal service to explain unavailability of the data due to guard dogs.