Perhaps you should try some spelling variations:
thanh tai » thanh hai, thanh toan, doanh tai
thanh tap » thanh lap, thanh tay, thanh tam
cua viet » hoa viet, cua vat, cua dieu
sach ty » sach y, sach tu, sach thu
tu sach » thu sach, su sach, te sach
hac duc » hoc duc, ha duc, thach duc
hieu va » lieu va, hieu qua
ty nang » ky nang, ty xang, ty hang
ca viet » va viet, co viet, hoa viet
va hac » van hac, va khac, va cac
nang o » nang co, nang ho, nang ro
o hai » co hai, so hai, o lai

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 ty nang o hai. hieu va hac duc va ((thanh tap) OR (thanh tai)) ((cua viet) or (ca viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang o hai. hieu va hac duc va ((thanh tap) OR (thanh tai)) ((cua viet) OR (ca viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang o hai. hieu va hac duc va ((thanh tap) OR (thanh tai)) ((cua viet) or (ca viet))".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang o hai. hieu va hac duc va ((thanh tap) OR (thanh tai)) ((cua viet) or (ca viet))*.