Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
dua tren » dung tren
hieu van » hieu va, thien van, lieu va
truc va » thuc va, thuc vat, trung va
ba truc » cau truc, ba trung, dai truc
sach ky » sac ky, sach y, sach ty
so sach » so sanh, bo sach, co sach
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va
van ba » van ban, van bao, van bac

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky ((nang xa) OR (nang ma)) hoi. hieu van ba truc va dan vi ((dua tren) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky ((nang xa) OR (nang ma)) hoi. hieu van ba truc va dan vi ((dua tren) OR (cau tren))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky ((nang xa) OR (nang ma)) hoi. hieu van ba truc va dan vi ((dua tren) or (cau tren))*".