Perhaps you should try some spelling variations:
layer chromatographic » gas chromatographic, paper chromatography, der chromatographie
layer chromatography » gas chromatography, liquid chromatography
date chromatography » dye chromatography, native chromatography, paper chromatography
think layer » thin layer, thick layer, think later
think date » think data, think later, thinks data

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (((( think layer chromatographic ) OR ( think layer chromatography ))) OR ( think date chromatography )).
• Adding a wildcard symbol may retrieve word variants: (((( think layer chromatographic ) or ( think layer chromatography ))) or ( think date chromatography ))*.