A: The 3rd edition (published 1969) is likely in the public domain in some jurisdictions, but not all. Check your local copyright laws (typically life of author + 70 years – Strahler died in 2002, so his works are protected until 2072 in the US). The safest legal route is borrowing via the Internet Archive.
These modern editions (often titled Introducing Physical Geography or Physical Geography: Science and Systems of the Human Environment ) incorporate: physical geography arthur n strahler pdf