Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
tru nang » tra nang, tri nang, truc nano
hieu van » hieu va, thien van, lieu va
tu sach » su sach, te sach, tu cach
va dang » van dang, va nang, da dang
va lang » va nang, hoa lang
van hac » van hoc, van ha, van hai
hac xuc » chat xuc
nang xa » nang x, lang xa, nang ma
hai va » hai van, thai va, hoi va
thiet » thieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (thu sach)) tru nang xa hoi. hieu van hac xuc ((va dang) OR (va lang)) hai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) tru nang xa hoi. hieu van hac xuc ((va dang) OR (va lang)) hai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu sach)) tru nang xa hoi. hieu van hac xuc ((va dang) OR (va lang)) hai va thiet".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) tru nang xa hoi. hieu van hac xuc ((va dang) OR (va lang)) hai va thiet*.