Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
nhan tai » hang tai, van tai, toan tai
toc sach » hoc sach, doc sach, thuoc sach
tu sach » thu sach, su sach, te sach
va tham » van tham, va cham, va thanh
va nhan » van nhan, ca nhan, va phan
thuc va » thuc vat, thuc dan, thuc day
tang ma » mang may, tang van
hieu va » lieu va, hieu qua
cuc te » cua te, cuc thue, cuc tieu

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 (toc sach)) ky ((nang x) or (tang ma)) hoi. hieu va tham thuc va nhan tai cuc te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (toc sach)) ky ((nang x) OR (tang ma)) hoi. hieu va tham thuc va nhan tai cuc te.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (toc sach)) ky ((nang x) or (tang ma)) hoi. hieu va tham thuc va nhan tai cuc te*.