Abendlied & Märchenfarben :
for accordion ensemble, optional choir, and percussiongroup [sic] /
Per Nørgård.

APA Citation

Nørgård, P., Wölfli, A. (1990). Abendlied & Märchenfarben: for accordion ensemble, optional choir, and percussiongroup [sic]. Copenhagen: Edition W. Hansen.

MLA Citation

Nørgård, Per, 1932-, and Adolf Wölfli. Abendlied & Märchenfarben: for Accordion Ensemble, Optional Choir, And Percussiongroup [sic]. Copenhagen: Edition W. Hansen, 1990.

Warning: These citations may not always be complete (especially for serials).