Perhaps you should try some spelling variations:
sectional studies » functional studies, regional studies, sectional study
doctoral studies » doctoral students, doctoral student, cultural studies
balkans regional » balkan regional, balkan region, balkans national
lanka regional » lanea regional, batka regional, panama regional
linear regions » line regions, linear relations, linear response
world balkans » world bank's, world banana, world banks
world linear » world line, world lines, world nonlinear
world lanka » world bank, world banks, world lack

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: (( world lanka regional AND doctoral studies ) OR ((( world linear regions AND sectional studies ) OR ( world balkans regional AND sectional studies )))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( world lanka regional and doctoral studies ) OR ((( world linear regions and sectional studies ) OR ( world balkans regional and sectional studies ))))".
• Adding a wildcard symbol may retrieve word variants: (( world lanka regional and doctoral studies ) OR ((( world linear regions and sectional studies ) OR ( world balkans regional and sectional studies ))))*.