Instructions: In this task, we ask you to elaborate the sentence without changing its general meaning. You can do so by explaining further the input sentence, using more precise wording, adding qualifiers and auxiliary information etc.
Input: The national ISBN agency assigns the publisher number ( cf. the ) ; the publisher selects the item number .
Output:
The national ISBN agency assigns the registrant element ( cf . ) and an accompanying series of ISBNs within that registrant element to the publisher ; the publisher then allocates one of the ISBNs to each of its books .