Vahervuo, Toivo <br/><br/>
Pupils' Arithmetical Ability :   Differences Due to the Teacher. A methodological Approach 

 - Helsinki :   Suomalainen Tiedeakatemia,   1957. 
 - 48 p. ;   18 cm. 
 - Annales Academiae Scientiarum Fennicae. Ser. B. ;   T. 107, 2 .