Perhaps you should try some spelling variations:
may khoa » da khoa, ly khoa, y khoa
hieu van » hieu va, thien van, lieu va
va lang » va nang, hoa lang
va hang » van hang, va nang, va hanh
cau hoa » cau hoi
van cau » van dau, van hau, van chat
sach ky » sach y, sach ty, sach kem
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky
de cua » le cua, te cua, dieu cua

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 (sac ky)) mang may khoa. hieu van cau hoa ((va hang) or (va lang)) de cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sac ky)) mang may khoa. hieu van cau hoa ((va hang) OR (va lang)) de cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) OR (sac ky)) mang may khoa. hieu van cau hoa ((va hang) or (va lang)) de cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sac ky)) mang may khoa. hieu van cau hoa ((va hang) or (va lang)) de cua tre*.