$l2h_cache_key = q/$$\partial_t \eta (t) = g(\eta(t),\varphi(t))$$ ''/; $l2h_cache{$l2h_cache_key} = q|

\begin{displaymath}\partial_t \eta (t) = g(\eta(t),\varphi(t))\end{displaymath}

”|; $l2h_cache_key = q/$--a {\frac{1}{2}} @minus{}$/; $l2h_cache{$l2h_cache_key} = q| $--a {\frac{1}{2}} @minus{}$|; $l2h_cache_key = q/$--a@minus{} {\frac{1}{2}}$/; $l2h_cache{$l2h_cache_key} = q| $--a@minus{} {\frac{1}{2}}$|; 1;