Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
sach tay » xach tay, sach hay, sach nay
cau tren » cu tren, dau tren, ca tren
tay tang » tay lang, tay trung, tay quang
tang ma » mang may, tang van
hieu va » lieu va, hieu qua
va tham » van tham, va cham, va thanh
va hanh » van hanh, va thanh, ban hanh
va danh » va dinh, va dan, dia danh
te sach » toc sach
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 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 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 tang ma hoi. hieu va tham thuc ((va hanh) or (va danh)) vi cau tren*.