Without prejudice to the prescripts of cann. 37 and 51, when a very grave reason prevents the handing over of the written text of a decree, the decree is considered to have been made known if it is read to the person to whom it is destined in the presence of a notary or two witnesses. After a written record of what has occurred has been prepared, all those present must sign it.
Source: Code of Canon Law (Vatican.va)