While originally designed for general music students, this book is arguably the "bible" for percussionists. The exercises are often performed by clapping (palmas) or tapping on a surface. This practice builds the coordination required for battery percussion and drum set playing.

If you cannot locate Rifo's PDF, these resources provide identical training in rhythmic reading:

The by Guillermo Rifo Suárez is a foundational method focused on rhythmic reading for popular music. While the full original text published by the Chilean Ministry of Education is approximately 135–136 pages long, specific digital versions and fragments are frequently cited by page count or "pdf 23" shorthand in academic and music forums. Where to Find the Manual

If you are looking for "23" because you are stuck on a specific exercise, you are likely dealing with the challenge of uneven groupings. A 5/8 time signature, for instance, cannot be divided evenly into two or three equal parts without leaving a remainder.

(PDF) Manual de Solfeo Ritmico Guillermo Rifo - Academia.edu