Complex sentence: In sentiment, scope, overall conception, and many particulars, Longfellow's poem is very much a work of American Romantic literature, not a representation of Native American oral tradition, despite Longfellow's insistence that I can give chapter and verse for these legends.
Split into simpler sentences: In sentiment, scope, overall conception, and many particulars, Longfellow's poem is very much a work of American Romantic literature, not a representation of Native American oral tradition. Longfellow insisted, I can give chapter and verse for these legends.