coupling {<coupling-statement>} end

<coupling-statement> :==

  assign <atom-selection> <atom-selection> <atom-selection> <atom-selection> 
        [<atom-selection> <atom-selection> <atom-selection> <atom-selection>]
         <real> <real> [<real> <real>]
  --{Atom-i  atom-j  atom-k  atom-l  J-obs  J-err.
     Optional second set of selections and observations is 
     for multiple classes.}
  class=<classname>
  --{Starts a new class which applies to all assignment, coefficient, 
     force, and potential entries until another class entry is issued.}
  coefficients <real> <real> <real> <real>
  --{Set the Karplus curve coefficients a, b, c and the 
     Karplus curve phase p (in that order) for this class.}
  cv=<integer>
  --{Select partition number for cross-validation.}
  force <real> [<real>]
  --{Force constant(s) for all assignments in the current class.
     Default = 50 [10].}
  nrestraints=<integer>
  --{Number of slots for J coupling restraints to allocate in memory.
     Default = 200.}
  partition=<integer>
  --{Number of partitions for complete cross-validation.}
  potential=square|harmonic|multiple
  --{Potential type for this class.}
  print threshold <real> all|class=<classname>
  --{Print J coupling violations greater than the specified value (in Hz).}
  reset
  --{Erase the J coupling assignment table, but keeps nrestraints the same.}