Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh tai » thanh tai, hang tai, han tai
tru nang » tra nang, tri nang, truc nano
hanh dai » hanh dao, vanh dai, thanh dat
tu nang » tu nong, tu nano, tu lang
cao suc » cao su, cao duc
va cao » va cac, va co, va dao
suc xa » tuc xa, buc xa, suc ma
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: toc sach ((tu nang) or (tru nang)) xa hoi. lieu va cao suc xa ((hanh dai) OR (hanh tai)) va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((tu nang) OR (tru nang)) xa hoi. lieu va cao suc xa ((hanh dai) OR (hanh tai)) va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((tu nang) or (tru nang)) xa hoi. lieu va cao suc xa ((hanh dai) OR (hanh tai)) va thiet".
• Adding a wildcard symbol may retrieve word variants: toc sach ((tu nang) or (tru nang)) xa hoi. lieu va cao suc xa ((hanh dai) OR (hanh tai)) va thiet*.