Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hieu van » hieu va, thien van, lieu va
manh hai » lanh hai, minh hai, thanh hai
danh hai » dang hai, lanh hai, danh hau
cam tuc » cam xuc, cam tu, nam thuc
su sach » so sach, vu sach
nang ma » tang ma, sang ma, mang may
van cam » van nam, van lam, van cau
sach v » sach va, sach y, sach 2
tuc va » thuc va, truc va, tuc xa

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 v ((nang ma) or (nang cao)) hoi. hieu van cam tuc va ((danh hai) OR (manh hai)) cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach v ((nang ma) OR (nang cao)) hoi. hieu van cam tuc va ((danh hai) OR (manh hai)) cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach v ((nang ma) or (nang cao)) hoi. hieu van cam tuc va ((danh hai) OR (manh hai)) cau tren".
• Adding a wildcard symbol may retrieve word variants: su sach v ((nang ma) or (nang cao)) hoi. hieu van cam tuc va ((danh hai) OR (manh hai)) cau tren*.