Alto Recorder Duet Collection 1: From Bach's Works, Edited by Fumio Kitamikado

This is a duet sheet music collection for alto recorder.
It includes works by Bach. Please check photos 4 and 5, which show the table of contents, for the song list.
There are stains on the front and back covers.
The back cover also has sun fading, but the music itself is clean with no dirt or stains.
Published by Zen-On Music Company Ltd.

Thank you for looking.