Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hieu cua » hieu qua, dieu cua, bieu cua
anh tay » canh tay, anh ta, anh hay
tay hoi » tay ho, tao hoi, tay thai
cac hoc » cach hoc, cac hop, bac hoc
va hanh » van hanh, va thanh, va danh
va dinh » van dinh, va kinh, va tinh
sac ky » sai ky
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: tu ((sac ky) or (cac ky)) anh tay hoi. hieu cua cac hoc ((va hanh) or (va dinh)) vi cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sac ky) OR (cac ky)) anh tay hoi. hieu cua cac hoc ((va hanh) OR (va dinh)) vi cau tren.
• Adding a wildcard symbol may retrieve word variants: tu ((sac ky) or (cac ky)) anh tay hoi. hieu cua cac hoc ((va hanh) or (va dinh)) vi cau tren*.