Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
cau tren » cu tren, dau tren, ca tren
sach tay » xach tay, sach hay, sach tai
sach nay » sach hay, sach vay, sach nang
va danh » va dinh, va dan, dia danh
va hanh » van hanh, va thanh, ban hanh
hieu va » lieu va, hieu qua
tang ma » mang may, tang van
va tham » van tham, va cham, va thanh
ma hoi » mai hoi, xa hoi, ma hoa
vi cau » va cau, ve cau, di cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: te ((sach tay) OR (sach nay)) tang ma hoi. hieu va tham thuc ((va hanh) or (va danh)) vi cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach tay) OR (sach nay)) tang ma hoi. hieu va tham thuc ((va hanh) OR (va danh)) vi cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach tay) OR (sach nay)) tang ma hoi. hieu va tham thuc ((va hanh) or (va danh)) vi cau tren".
• Adding a wildcard symbol may retrieve word variants: te ((sach tay) OR (sach nay)) tang ma hoi. hieu va tham thuc ((va hanh) or (va danh)) vi cau tren*.