On period polynomials of degree $2^m$ for finite fields
  We obtain explicit factorizations of reduced period polynomials of degree $2^m$, $m\ge 4$, for finite fields of characteristic $p\equiv 3$ or $5\pmod{8}$. This extends the results of G. Myerson, who considered the cases $m=1$ and $m=2$, and S. Gurak, who studied the case $m=3$. 
Ioulia N. Baoulina
math.NT