Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
tru nang » tra nang, tri nang, truc nano
hanh tai » thanh tai, hang tai, han tai
va triet » va thiet, va trien, ve triet
tu nang » tu nong, tu nano, tu lang
cac tuc » cac toc, cac tu, cac tac
xa hanh » xa thanh, xa khanh, va hanh
tai va » thai va, mai va, tri va

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) OR (doc sach)) ((tu nang) or (tru nang)) xa hoi. lieu va cac tuc xa hanh tai va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ((tu nang) OR (tru nang)) xa hoi. lieu va cac tuc xa hanh tai va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) ((tu nang) or (tru nang)) xa hoi. lieu va cac tuc xa hanh tai va triet".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (doc sach)) ((tu nang) or (tru nang)) xa hoi. lieu va cac tuc xa hanh tai va triet*.