Lyttkens, Ejnar <br/><br/>
Problems of Dark Nebulae, Treated by the Method of Moments 

 - Upsala :   Almquist & Wiksell,   1950. 
 - 88 p. ;   15 cm. 
 - Nova Acta Regiae Societatis Scientiarum Upsaliensis. Uppsala Astronomiska Observatoriums Annalar, Band 2 ;   Nš 9 .