converting finite field elements to octet strings I need to convert elements of the finite field $GF(p^k)$, where $p$ is an odd prime, to octet strings.

To be more precise, I want to include elliptic curve points over $GF(p^2)$ in a Subject Public Key Info of an X.509 certificate.
In the document IEEE P1363 there is a FE2OSP function which is probably not usable for that case. 

Do you know of any well accepted standard which describes that encoding?
Ok,
if there is no standard, then "I do it my way":

Let $i$ be a root of a fixed minimum polynomial of $GF(p^2)$ and $x$ be an element in $GF(p^2)$. Then $x:= x_1+x_2*i$ can be represented as a vector $(x_1,x_2) \in GF(p)^2$. 
Now convert $x_1$ and $x_2$ with the FE2OSP function form IEEE P1363 and concatenate them
$FE2OSP(x_1)|| FE2OSP(x_2)$.  

An elliptic curve point $(x,y) \in E(GF(p^2))$ can then be represented either compressed or not compressed.

not compressed:  


$04|| FE2OSP(x_1)|| FE2OSP(x_2)|| FE2OSP(y_1)|| FE2OSP(y_2)$


compressed:


$02|| FE2OSP (x_1)|| FE2OSP (x_2)$ if $LSB(FE2OSP(y_1))=0$
$03|| FE2OSP(x_1)|| FE2OSP (x_2)$ if $LSB(FE2OSP (y_1))=1$