Prove that $A=\{wtw^R|w,t\in \{0,1\}^*\wedge |w|=|t|\}\notin CFG$
I use pumping lemma:
Let $p$ will be length of pumping.Given $s=1^p0^p1^p=uvxyz $
We know, that (because of the fact that $|vxy|\le p$):
$vxy\in 1^k0^l$
$vxy\in 0^p$
$vxy\in 1^p$
$vxy\in 1^k0^l$
It is sufficient to pump down ($v^0y^0$), and we violent contraint that every of three part has the same length.
It is my solution. What about other ideas ?