Singer, Ivan. <br/><br/>
Best approximation in normed linear spaces by elements of linear subspaces   
by Ivan Singer 
 - New York  Springer Verlag  1970 
 - 415p. 
 - Die Grundlehren der mathematischen Wissenschaften  Band 171 .
<br/><br/><label>LCCN: </label>73-110407 
<br/><br/><label>Dewey Class. No.: </label>514.3  / N705;2