Every element of  <I>F</i>(<i>a</i>) can be uniquely expressed in the form
<I>c<sub>n -1</sub>a<sup> n-1</SUP> + c<sub>n -2</sub>a<sup> n-2</SUP> + ... + c<sub>1</sub>a  + <I>c<sub>0</I>,
<BR> where
<I>c<sub>n -1</sub>,   c<sub>n -2</sub>,..., c<sub>1</sub>, <I>c<sub>0</sub> &#8712 F</I>.