let $k$ be a field of characteristic$p>0$, $k[[x]]$, the ring of formal power series over $ k$,$k((x))$, the quotient field of $ k[[x]]$, and $ k(x)$ the fieldof rational functions over $k$. we shall give somecharacterizations of an algebraic function $fin k((x))$ over $k$.let $l$ be a field of characteristic zero. the power series $finl[[x]]$ is called differentially algebraic, if it satisfies...

Abstract The Arenig Fawr area of North Wales constitutes the type for British Lower to Middle Ordovician Series and is complemented by sections in Carmarthen Whitland areas South Wales. We describe chitinozoan assemblages from both order aid correlation its region with global series stages. Chitinozoans recorded provide permissive rather than conclusive evidence but suggest that Henllan Ash Mem...