reference.autolabel
list 
0none
11,2,3...
AA,B,C...
aa,b,c...
ii,ii,iii...
II,II,III...
reference.autolabel
Specifies the labeling format for Reference titles
  I
Description
If non-zero, references will be numbered using the parameter
  value as the number format if the value matches one of the
  following:
  
    1 or arabic
    
      Arabic numeration (1, 2, 3 ...).
    
  
  
    A or upperalpha
    
      Uppercase letter numeration (A, B, C ...).
    
  
  
    a or loweralpha
    
      Lowercase letter numeration (a, b, c ...).
    
  
  
    I or upperroman
    
      Uppercase roman numeration (I, II, III ...).
    
  
  
    i or lowerroman
    
      Lowercase roman letter numeration (i, ii, iii ...).
    
  
Any non-zero value other than the above will generate
the default number format (upperroman).