YU 
EXPLANATORY. 
This Volume is printed in the Divisions enumerated on p. viii. 
The pagination of each Division is separate, and is given at the 
left-hand top corner of the pages. The number and name of the 
Division is given as a heading on each page. The date 1921 
corresponding to the bulk of the literature indexed is given at 
the top of each page. 
In the Subject Index of each Division authors are quoted by name 
only. The full references will be found in the Title Section of the 
Division. 
The Literature indexed is mainly that of 1921 but includes entries 
for earlier years that have been received too late for inclusion in 
previous volumes. 
