Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help besa2fieldtrip”.

  BESA2FIELDTRIP reads and converts various BESA datafiles into a FieldTrip
  data structure, which subsequently can be used for statistical analysis
  or other analysis methods implemented in Fieldtrip.
 
  Use as
    [data] = besa2fieldtrip(filename)
  where the filename should point to a BESA datafile (or data that
  was exported by BESA). The output is a MATLAB structure that is
  compatible with FieldTrip.
 
  The format of the output structure depends on the type of datafile:
    *.avr is converted to a structure similar to the output of FT_TIMELOCKANALYSIS
    *.mul is converted to a structure similar to the output of FT_TIMELOCKANALYSIS
    *.swf is converted to a structure similar to the output of FT_TIMELOCKANALYSIS (*)
    *.tfc is converted to a structure similar to the output of FT_FREQANALYSIS     (*)
    *.dat is converted to a structure similar to the output of FT_SOURCANALYSIS
    *.dat combined with a *.gen or *.generic is converted to a structure similar to the output of FT_PREPROCESSING
 
  Note (*): If the BESA toolbox by Karsten Hochstatter is found on your
  MATLAB path, the readBESAxxx functions will be used (where xxx=tfc/swf),
  alternatively the private functions from FieldTrip will be used.
 
  See also EEGLAB2FIELDTRIP, SPM2FIELDTRIP