Free public domain sheet music from IMSLP / Petrucci Music Library
Creative Commons Attribution 3.0 [tag/del]
This is a chanson from a 1569 publication which I am assuming is the 6th not the 9th book. A complete modern edition of Arcadelt's works is published in CMM, xxxi, 1-10 (ten volumes), edited by Albert Seay so it may be possible to sort out which book it is for certain.
||Je ne suis pas si sot
||1569 in Sisième livre de chansons