Perhaps you should try some spelling variations:
phan thi » pham thi, tran thi, phan tu
phan tai » pham tai, nhan tai, han tai
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
duc van » duc va, duc tan, duc manh
cau duc » cao duc, cau luc, chu duc
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
nang xa » nang x, nang ma, mang xa
va cau » van cau, va cac, va dau
cuc tu » cuc du, luc tu, duc tu

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 ky ((nang xa) or (lang xa)) hoi. hieu va cau duc van ((phan tai) OR (phan thi)) cuc tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang xa) OR (lang xa)) hoi. hieu va cau duc van ((phan tai) OR (phan thi)) cuc tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((nang xa) or (lang xa)) hoi. hieu va cau duc van ((phan tai) OR (phan thi)) cuc tu".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang xa) or (lang xa)) hoi. hieu va cau duc van ((phan tai) OR (phan thi)) cuc tu*.