Lattice graphics and strip function

I am looking for examples of code that demonstrates the
fine tuning of the strip panels in lattice graphics and
uses plotmath characters.  The code for the graphic is as
follows:



xyplot(lagy ~ n | rho1 * rho2, data= data, layout=c(2,6),
span = 1,

xlab = "Sample Size", ylab = "Bias in the Coefficient for
the Lag of X",

type = "o")



rho1 is a four level factor and rho2 is a three level
factor.



The problem is that I want to use plotmath characters in
the strips, but using the strip = function the best I so
far have been able to do is change all the strip labels
to the same character instead of it varying as the
factors do.  Since I am using plotmath characters I am
unable to change how R designates the factors which would
be the easiest solution. I have read the documentation
several times and am unable to decipher how to set the
parameters for the strip function.