In FrameMaker, a non-breaking space can only be inserted using "\ " (backslash and space). In Trados Studio you need to do the same, since a regular non-breaking space (Ctrl+Shift+Space) is removed in a target MIF file. Due to the fact it is not possible to define RegEx verification criteria for specific Document Structure Elements only, this means it must be checked manually if the translator used the requested alternative for a non-breaking space. This would not be necessary if Trados Studio would write backslash and space in the variables and reference names in target file instead of removing it.