How did the American entrance into World War One turn the tide for the Allies?

According to documents in wiesner et al., why has access to water been such an important factor in the rise of complex societies? how did ancient societies address the problems associated with harnessing these powerful resources? how have historians assessed and addressed this issue? cite the appropriate documents relevant to the response.

What kind os source would a historian use to get a firsthand account of a past event

Which statement best describes a contribution of the works of nicolas copernicus and galileo galilei?