What does cfr. stand for? In a article I saw this expression:


  ... initial sample (cfr. Härdle et al. (2004))...


What is the meaning of cfr. or does it stands for?
Cfr is the abbreviation of the Latin imperative confer, which means compare with.
The common English abbreviation is cf.

Your citation can be found in this document, which is written by a Spanish group. A search of the Oxford Spanish Dictionary yields:


  cf.
  
  1 Abreviatura del imperativo latino confer, 'compara' o 'consulta',
  que se utiliza en escritos para remitir a un párrafo o libro que
  contiene información relacionada con el tema tratado. 
  
  Usage 
  
  También se abrevia cfr


The last sentence tells you that in Spanish cf is sometimes abbreviated as cfr.