Original sentence: Hippocrates, Galen, Pliny the Elder, and others knew that willow bark could ease pain and reduce fevers.It was used in Europe and China to treat these conditions.The Cherokee and other Native Americans use an infusion of the bark for fever and other medicinal purposes.This remedy is mentioned in texts from Ancient Egypt, Sumer, and Assyria
Edited sentence: Many authors have claimed that Hippocrates, Galen, Pliny the Elder, and others knew that willow bark could ease pain and reduce fevers, but the evidence for this is weak, and it is difficult to find the relevant quote in translations of Hippocrates,  Celsus or Dioscorides.There have also been claims of its use in China, Ancient Egypt, Sumer, Assyria and America,  but to conclude that the ancients had effectively discovered aspirin would be speculation