Perhaps you should try some spelling variations:
khan thong » khap thong, khau thong, nhan thong
phu thong » pho thong, phap thong, khau thong
sach dao » lanh dao
kho khan » khoa kham, khoa than
sach tai » sach bai, sach tham, sach xa
tai thuc » thai thuc, tri thuc, dai thuc
thuc cac » thuc cach, tuc cac, phuc cac
cac khoa » cac khoan, cac khoi, dac khoa
khoa phu » khoa phau, khoa thu, hoa phu
tu sach » thu sach, te sach, tu cach
dac kho » dac khoa, dac khao, dac cho
su sach » so sach, vu sach
dao tu » dao tuc, dao tru, tao tu
tu dac » thu dac, tu cac, tu dat

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 dao tu dac kho khan thong ) or ( su sach tai thuc cac khoa phu thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach dao tu dac kho khan thong ) OR ( su sach tai thuc cac khoa phu thong )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach dao tu dac kho khan thong ) or ( su sach tai thuc cac khoa phu thong ))*.