Enumerations for _Chem_shift_ref.External_ref_loc (An open enumeration)
`insert at center of a separate sample tube` | enumeration_text
`insert at center of experimental sample tube` | enumeration_text
`insert at outer edge of a separate sample tube` | enumeration_text
`insert at outer edge of experimental sample tube` | enumeration_text
`other` | enumeration_text
`separate tube (no insert) not similar to the experimental sample tube` | enumeration_text
`separate tube (no insert) similar to the experimental sample tube` | enumeration_text