Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
cam truc » cau truc, nam truc, lam truoc
cau tren » cu tren, ca tren, cau treo
hang tai » hang va, dung tai
va hang » van hang, va nang, va lang
truc va » thuc va, thuc vat, trung va
hieu ve » hieu va, hieu van
nang ma » tang ma, sang ma, nang cao
ve cam » ve cham, ve cac, va cam
can ky » van ky, dan ky, ban ky
tu can » tu ban, tu cac, thu canh

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu can ky ((sang tao) or (nang ma)) hoi. hieu ve cam truc va hang tai ((cau tren) OR (dau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu can ky ((sang tao) OR (nang ma)) hoi. hieu ve cam truc va hang tai ((cau tren) OR (dau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu can ky ((sang tao) or (nang ma)) hoi. hieu ve cam truc va hang tai ((cau tren) OR (dau tren))".
• Adding a wildcard symbol may retrieve word variants: tu can ky ((sang tao) or (nang ma)) hoi. hieu ve cam truc va hang tai ((cau tren) OR (dau tren))*.