Bibliography 



The system for presenting bibliographic references used here has been adapted 

 from one in common use in geographic atlases. An item in a table is identified by two 

 coordinates, a letter designating the column, and a number the row, in which the item 

 appears. In a typical instance in the bibliography, the coordinates of an item are followed 

 in the column to the right, by a number accompanied by a small letter. The number refers 

 to the bibliographic source, the letter to the person contributing the item. If an item in a 

 table is based on another item from another part of the same table, the coordinates of the 

 latter are given as source, enclosed in parentheses. 



This method of presentation of bibliographic references perniits identification of 

 both the reference source of each item and the person contributing it, without the necessity 

 of use of reference numbers on the face of the table. The resulting saving in space per- 

 mits use of a larger type face in each table, with a consequent gain in readability. It is 

 not uncommon for some value in a table to be based on more than a single reference source. 

 The occurrence of such instances has given emphasis to the desirability of eliminating 

 reference numbers from the tables. 



Where an item is contributed as general knowledge, or from the unpublished investi- 

 gations of the contributor, a letter appears in the source column without accompanying 

 number. 



If bibliographic reference numbers are inclosed in brackets, [] , a letter designa- 

 tion of a contributor, immediately following the second bracket, applies to all references 

 within the brackets. 



It should be understood that a person listed as a contributor for any table is not 

 responsible for portions of the table other than as indicated. 



The following abbreviations are used: Fn = footnote; Calc. fr. = calculated from; 

 Av. = average. 



1. NlTrRIENTS: THE CHHtlCAL ELOffiNTS 



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257 



