I am familiar with the fact that there is a maklokes between poskim if one may daven mincha after shkia during "bein hashmoshos" (however long or what time one holds that to be.) However the opinions on either side of the maklokes are not known to me. Between the Rishonim and Achronim who holds that a person may daven mincha bein hashmoshos and who holds one may not. All of course this being "b'dieved" since one should certainly do their best to daven before shkia.
(This is not a duplicate of another similar question because here I am asking for the differing opinions on both sides of the matter and their sources.)