Casnati, Gianfranco http://orcid.org/0000-0001-9272-9074
Article History
Received: 8 June 2017
Accepted: 21 October 2017
First Online: 17 November 2017
Change Date: 20 February 2019
Change Type: Correction
Change Details: The proof of Theorem 1.2 in 2 contains a gap which can be filled by simply assuming that the base field <Emphasis Type="Italic">k</Emphasis> is uncountable.