Perhaps you should try some spelling variations:
dau tieng » dau tien, cau tieng, day tieng
dau tren » dau tien, dat tren, dau trong
cam truc » cau truc, nam truc, lam truoc
hanh va » hang va, hanh vi
nang ma » tang ma, sang ma, nang cao
hieu ve » hieu va, hieu van
truc va » thuc va, thuc vat, trung va
va hanh » van hanh, va thanh, va danh
tu van » tu va
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: tu van ky ((mang may) or (nang ma)) hoi. hieu ve cam truc va hanh va ((dau tren) OR (dau tieng))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu van ky ((mang may) OR (nang ma)) hoi. hieu ve cam truc va hanh va ((dau tren) OR (dau tieng)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu van ky ((mang may) or (nang ma)) hoi. hieu ve cam truc va hanh va ((dau tren) OR (dau tieng))".
• Adding a wildcard symbol may retrieve word variants: tu van ky ((mang may) or (nang ma)) hoi. hieu ve cam truc va hanh va ((dau tren) OR (dau tieng))*.