Perhaps you should try some spelling variations:
phan trac » phan cac, phan tan, hai trac
phan tap » phan lap, han tap, pha tap
van hanh » van thanh, van anh, van ban
ban hanh » ban hang
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
sang ma » tang ma, nang ma, sang tao
ky sang » ky nang, ky dang, ky tang
ma hoi » mai hoi, xa hoi, ma hoa
vi cua » vai cua, di cua

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 sang ma hoi. hieu van ((phan trac) OR (phan tap)) ((ban hanh) or (van hanh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky sang ma hoi. hieu van ((phan trac) OR (phan tap)) ((ban hanh) OR (van hanh)) vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky sang ma hoi. hieu van ((phan trac) OR (phan tap)) ((ban hanh) or (van hanh)) vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky sang ma hoi. hieu van ((phan trac) OR (phan tap)) ((ban hanh) or (van hanh)) vi cua tre*.