Data type: char
Must appear in a looped list
May match a value of '_diffrn_refln_standard_code' containing '_diffrn_standard_refln_index_'
The code identifying a reflection measured as a standard reflection with the indices _diffrn_standard_refln_index_. This is the same code as the _diffrn_refln_standard_code in the _diffrn_refln_ list.