This is a start. This booklet is for sale at the moment.
And the first edition of "Alfa Romeo GTA' written by Maurizo Tabucchi and published in 1994 by Giorgio Nada Editore also contains the Homologation papers for the GTA, GTA 1300 Junior and GTAm. I have an extra copy if you want one.
Of course 'Alleggerita' written by Tony Adriaensens and published in 1994 by Corsa research also contains the Homologation Papers but that book has become pretty expensive!