Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
hieu va » lieu va, hieu qua
dan hai » doan hai, dang hai, dan khai
thuc va » thuc vat, thuc dan, thuc day
va tham » van tham, va cham, va thanh
so sach » so sanh, co sach, hoc sach
nang ma » tang ma, sang ma, nang cao
ly nang » ky nang, ly hang, ly vang
bo sach » co sach, hoc sach
cu tren » tu tren, dua tren
ma hoi » mai hoi, xa hoi, ma hoa
va dan » ca dan, va dao, va dau
hai cu » hai cua, hai chu, hai cuc

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((so sach) or (bo sach)) ly nang ma hoi. hieu va tham thuc va dan hai cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((so sach) OR (bo sach)) ly nang ma hoi. hieu va tham thuc va dan hai cu tren.
• Adding a wildcard symbol may retrieve word variants: ((so sach) or (bo sach)) ly nang ma hoi. hieu va tham thuc va dan hai cu tren*.