Perhaps you should try some spelling variations:
"vakbond/mijnwerkers | syndicaat/mineurs" » "vakbond/mijnwerkers | syndicale/mineurs"
"vakbond/mijnwerkers | syndicales/mineurs" » "vakbond/mijnwerkers | syndicale/mineurs", "vakbond/mijnwerkers | syndicats/mineurs"
"vakbonden/mijnwerkers | syndicat/mineurs" » "vakbonden/mijnwerkers | syndicats/mineurs", "vakbonden/mijnwerkers | syndicale/mineurs"

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (((("vakbond/mijnwerkers | syndicaat/mineurs") OR ("vakbond/mijnwerkers | syndicales/mineurs"))) OR ("vakbonden/mijnwerkers | syndicat/mineurs"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"vakbond/mijnwerkers | syndicaat/mineurs\") OR (\"vakbond/mijnwerkers | syndicales/mineurs\"))) OR (\"vakbonden/mijnwerkers | syndicat/mineurs\"))".
• Removing quotes may allow a broader search: (((( vakbond/mijnwerkers | syndicaat/mineurs ) OR ( vakbond/mijnwerkers | syndicales/mineurs ))) OR ( vakbonden/mijnwerkers | syndicat/mineurs )).
• Adding a wildcard symbol may retrieve word variants: (((("vakbond/mijnwerkers | syndicaat/mineurs") OR ("vakbond/mijnwerkers | syndicales/mineurs"))) OR ("vakbonden/mijnwerkers | syndicat/mineurs"))*.