Full Idea
X knows a priori that p iff the belief was produced with an a priori warrant, which is a process which is available to X, and this process is a warrant, and it makes p true.
Gist of Idea
A priori knowledge comes from available a priori warrants that produce truth
Source
Philip Kitcher (The Nature of Mathematical Knowledge [1984], 01.4)
Book Reference
Kitcher,Philip: 'The Nature of Mathematical Knowledge' [OUP 1984], p.24
A Reaction
[compression of a formal spelling-out] This is a modified version of Goldman's reliabilism, for a priori knowledge. It sounds a bit circular and uninformative, but it's a start.