PREFACE 



This volume, completing the sixth year of the Agricuhural Index, is the 

 second three-year cumulation and covers the years 1919, 1920 and 1921. 



According to the regular plan of cumulation, this volume is published instead 

 of the annual volume for 1921. It contains references for the three years 1919- 

 1921 inclusive, and, therefore, supplants the annual volumes for 1919 and 1920. 

 It is now necessary to consult only two alphabets for references to all journals 

 indexed since 1916. 



There are now one hundred twenty-eight agricultural periodicals indexed 

 regularly. Seventy-eight journals were included at the end of the first three-year 

 period. The number continued the same thru the year 1919. In 1920, twenty- 

 two periodicals were added to the list, followed in 1921 by the addition of twenty- 

 eight more. 



Not all of the magazines on the present list are indexed, therefore, for the 

 full three-year period. Information, giving the volume numbers of the journals 

 indexed and the inclusive years covered, has been added in the "List of Periodicals 

 Indexed." 



A complete list of the regular bulletin and pamphlet material indexed in this 

 volume is included in the lists of experiment, department and extension literature 

 respectively. The "occasional material" indexed for the three years is listed in 

 the Checklist. 



Agricultural books were included for the first time during the year 1921. 

 They are listed in the main alphabet under subject, the difference in the form of 

 the entry, author followed by title, distinguishing them from the regular peri- 

 odical references. 



A department for critical reviews for a selected list of agricultural books 

 was begun in 1921. The reviews included for the year are cumulated in one 

 alphabet in this volume. 



Grateful acknowledgement is made to all those friends of the Agricultural 

 Index who have given of their assistance and advice during the three years ; to 

 Miss Zlaribel R. Barnett to whom we are indebted for the Agricultural Library 

 Notei each month; to Miss Hazel Lewis who has given invaluable assistance in 

 reading mc galley proofs for this volume and to Miss Irene Hartmann, Miss 

 Angelina Vasti and Miss Sophia Woods who have worked long and faithfully to 

 make this volume an accurate record. 



June, 1922. F. A. A. 



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