Systematic studies carried out since Keith's work have failed to replicate his periodization. Instead, other studies suggest that many companies exhibited a marketing orientation in the 19th century and that the business schools were teaching marketing decades before Pillsbury adopted a marketing-oriented approach. Jones and Richardson also investigated historical accounts of marketing practice and found evidence for both the sales and marketing era during the so-called production era and concluded that there was no 'marketing revolution.' Keith's eras have become known, somewhat cynically, as the "standard chronology". In spite of such criticisms, Keith's descriptions of the different eras continue to influence marketing thought.