24 Studies, Op. 21 (Studies and Etudes) By Joachim Andersen, Published by Schott.

The Danish flautist and composer Andersen was one of the founder members of the Berlin Philharmonic, and for 10 years was the orchestra's 1st flute. He toured extensively (including Russia and America) and shared a platform with artists like Hans von Bülow and Joseph Joachim. In addition to his performing career he also wrote studies for flute, instructive as well as musically attractive, which have become part of the standard works used in teaching. 

Further pieces by Andersen for flute and piano have been published by Schott in The Andersen Collection (EA 748).