Addison's essays on the imagination were highly influential as distillations and reformulations of aesthetic philosophy. The notion of dualism is maintained throughout Freud's various reformulations of the drive-theory. Over the years, the hypercycle theory has experienced many reformulations and methodological approaches. Again the transition probability, the stochastic matrix and the Markov kernel are equivalent reformulations. Some chapters appear to be reformulations of ideas which appear throughout the "Discourses". Retraced restarts refer to the reformulations whereby a portion of the original utterance is duplicated. One of the company's larger product reformulations came in March 2011. Further reformulations for lead content also concluded. But significant reformulations in foods normally take many years. Introduced in 1957, it has undergone several reformulations including re-sizing and bread changes. Historical annual reformulations of the influenza vaccine are listed in a separate article. Over the years, many reformulations of calculus have been investigated for different purposes. Later reformulations allowed more dispersant to be contained (at a higher concentration) to be aerosolized. Subsequent centuries produced commentaries and reformulations continuing up to as late as the 20th century. Reformulations are in direct contrast to the child-utterance, which contained an error.