On row sequences of Pad\'e and Hermite-Pad\'e approximation

A survey of direct and inverse type results for row sequences of Pad\'e and Hermite-Pad\'e approximation is given. A conjecture is posed on an inverse type result for type II Hermite-Pad\'e approximation when it is known that the sequence of common denominators of the approximating vector rational functions has a limit. Some inverse type results are proved for the so called incomplete Pad\'e approximants which may lead to the proof of the conjecture and the connection is discussed.