Using LaTeX in WordPress

Comparison of free, on-the-fly, web based LaTeX equation compilers compares some of the services mentioned in Online LaTeX which offer compilation via a URL.

A couple of the services are unable to process the plus sign correctly, probably because the symbol is changed at some stage. In those cases + needs to be replaced by %2B, thus

Sitmo 
<img src="http://www.sitmo.com/gg/latex/latex2png.2.php?z=100&eq=z_t = \displaystyle\sum^p_{j=1}\phi_jz_{t-j}%2B\sigma_\epsilon\xi_t" alt="" />
gives

MathTran
<img src="http://mathtran.open.ac.uk/cgi-bin/mathtran?D=1;tex=z_t = \displaystyle\sum^p_{j=1}\phi_jz_{t-j}%2B\sigma_\epsilon\xi_t" alt="" />
gives

Similar changes may have to be made for other symbols, though it would be better if the services themselves could do the necessary translation.