sentences:  Stanford professor Sam Wineburg has publicly criticized Zinn's research.Reviewing a critique by Wineburg, reviewer David Plotnikoff credits Wineburg for showing that "["A People's History"] perpetrates the same errors of historical practice as the tomes it aimed to correct," for "Zinn's desire to cast a light on what he saw as historic injustice was a crusade built on secondary sources of questionable provenance, omission of exculpatory evidence, leading questions and shaky connections between evidence and conclusions," for which he provides many examples.Conservative author Daniel J. Flynn likewise charges Zinn with presenting biased history.