Nicholls, H. E. <br/><br/>
A pioneer Bucket dredge in Northern Nigeria. 

 - Londres-XXK :   The Institution of Mining and Metallurgy,   1916. 
 - p. 1-13 :   maps. 
 - Irregular 
 - No. 137(Feb.1916) 
 - Bulletin of the Institution of Mining and Metallurgy,  ;   No. 137 .
 - Reino Unido.   The Institution of Mining and Metallurgy,. .
<br/><br/><br/>Inglés.