Perhaps you should try some spelling variations:
vat thanh » dat thanh, gat thanh, tat thanh
cam thuc » am thuc, nam thuc, cam thu
hieu van » hieu va, thien van, lieu va
tang ma » mang may, tang van
sach ky » sac ky, sach y, sach ty
van cam » van nam, van lam, van cau
nang ma » sang ma, nang cao, mang may
va chua » vua chua, ca chua, va chu
su sach » so sach, vu sach
va cua » via cua, ca cua, ma cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky ((nang ma) or (tang ma)) hoi. hieu van cam thuc vat thanh ((va cua) or (va chua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang ma) OR (tang ma)) hoi. hieu van cam thuc vat thanh ((va cua) OR (va chua)) tre.
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang ma) or (tang ma)) hoi. hieu van cam thuc vat thanh ((va cua) or (va chua)) tre*.