1139.26—Availability of underlying data.
All underlying data used in preparation of the material outlined above shall be made available in the office of the party serving such verified matter during usual office hours for inspection by any party of record desiring to do so, and shall be made available to the Board upon request therefor. The underlying data shall be made available also at the hearing, but only if, and to the extent, specifically requested in writing and required by any party for the purpose of cross-examination.