Popper 15 Easy Studies 2 cellos
IMC# 2551 15 Easy Studies edited by G. Woerl is one of two IMC editions. This has a Cello II ad lib part for Studies 1-10. Parts are in one book in score form.
*IMC# 3705 is the newer edition based on this one, in which Carter Enyeart which adds the Cello II part for Studies 11-15. The font is smaller, but there are measure numbers at the start of each line.