Full paper in PDF:
$%M. I. Ostrovskii, On prequojections and their duals, Rev. Mat. Complut. 11 (1998), no. 1, 59–77.%$

The paper is devoted to the class of Fréchet spaces which are called prequojections. This class appeared in a natural way in the structure theory of Fréchet spaces. The structure of prequojections was studied by G. Metafune and V. B. Moscatelli, who also gave a survey of the subject. Answering a question of these authors we show that their result on duals of prequojections cannot be generalized from the separable case to the case of spaces of arbitrary cardinality. We also introduce a special class of prequojections, we call them canonical, and show that in the main result of G. Metafune and V. B. Moscatelli on the existence of a prequojection with a given dual we may require this prequojection to be a canonical one.

1991 Mathematics Subject Classification: 46A13, 46A20, 46B10.