Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
sach ky » sac ky, sach y, sach kem
sach ty » sach y, sach tu, sach thu
cao hoi » cau hoi, co hoi, cao hoc
hieu ve » hieu va, hieu van
dan cua » dan ca, ban cua, day cua
ve cam » ve cham, ve cac, va cam
cam tu » cam thu, nam tu, dam tu

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

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