The mistake that the author made in using an in-text citation is:
An in-text citation is a reference to a quotation made by an author on a certain page of his book.
Often there is a separate bibliography underneath the text that contains the full name of the author, the book's title, year, of publication, and publisher.
There was no need for the author of the text above to restate the source's author because that will cause a redundancy.
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