Perhaps you should try some spelling variations:
vat hanh » vat thanh, van hanh, nhat hanh
cam thuc » am thuc, nam thuc, cam thu
cau tren » dau tren, ca tren, cau treo
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
va hanh » van hanh, va thanh, va danh
cu tren » tu tren, dua tren
y nang » ky nang, ly nang, v nang
ve cam » ve cham, ve cac, va cam

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 y nang x ho. hieu ve cam thuc ((vat hanh) OR (va hanh)) da ((cau tren) or (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y nang x ho. hieu ve cam thuc ((vat hanh) OR (va hanh)) da ((cau tren) OR (cu tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y nang x ho. hieu ve cam thuc ((vat hanh) OR (va hanh)) da ((cau tren) or (cu tren))".
• Adding a wildcard symbol may retrieve word variants: su sach y nang x ho. hieu ve cam thuc ((vat hanh) OR (va hanh)) da ((cau tren) or (cu tren))*.