The Linton theorem revisited
Hu's Primal Algebra Theorem revisited
It is shown how Lawvere's one-to-one translation between Birkhoff's description of varieties and the categorical one (see [6]) turns Hu's theorem on varieties generated by a primal algebra (see [4], [5]) into a simple reformulation of the classical representation theorem of finite Boolean algebras as powerset algebras.
On corings and comodules
It is shown that the categories of -coalgebras for a commutative unital ring and the category of -corings for some -algebra as well as their respective categories of comodules are locally presentable.
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