The search terms you provided—specifically including "PDF," "21," and "hot"—frequently appear on websites that host pirated or unauthorized digital copies of copyrighted textbooks . Horst Kuchling's " Taschenbuch der Physik
, is a seminal German-language reference work widely regarded as the "standard" for students and professionals in science and engineering. The 21st edition
If you are looking for the most up-to-date information, be aware of the edition.
: Includes the latest physical constants and updated material values.