The late 1960s saw a marked shift in the taxonomic treatment of this group, with the publication of four systems that would remain influential for the best part of the century, and which predominantly used the concept of superorder. These were the systems of Armen Takhtajan (1910–2009), Arthur Cronquist (1919–1992), Robert Thorne (1920–2015) and Rolf Dahlgren (1932–1987). In 1964 Zabinkova proposed formal rules for naming taxa above the rank of order, where superorders would end with the suffix "-anae". In the same issue of Taxon Takhtajan utilised those suggested rules to outline a coherent hierarchical supraordinal classification, as follows.