216 	r\backslash s = r_1 + r_2 + r_3 + \ldots + r_n,

   216 	r\backslash s = r_1 + r_2 + r_3 + \ldots + r_n,

   217 \]

   217 \]

   218 if we omit the way these regular expressions need to be nested.

   218 if we omit the way these regular expressions need to be nested.

   219 where each $r_i$ ($i \in \{1, \ldots, n\}$) is related to some fragments

   219 where each $r_i$ ($i \in \{1, \ldots, n\}$) is related to some fragments

   220 of $r$ and $s$.

   220 of $r$ and $s$.

   221 The second important observation is that the list %of regular expressions

   226 The second important observation is that the list %of regular expressions

   222 $[r_1, \ldots, r_n]$ %is not

   227 $[r_1, \ldots, r_n]$ %is not

   223 cannot grow indefinitely because they all come from $r$, and derivatives

   228 cannot grow indefinitely because they all come from $r$, and derivatives

   224 of the same regular expression are finite up to some isomorphisms.

   229 of the same regular expression are finite up to some isomorphisms.

   225 We prove that the simplifications of $\blexersimp$ %make use of 

   230 We prove that the simplifications of $\blexersimp$ %make use of