Perhaps you should try some spelling variations:
khan thong » khap thong, khau thong, nhan thong
thuc cach » thuoc sach, truoc cach, thuc hanh
cach khoa » bach khoa, cac khoa, cac khoan
pho thong » he thong
sanh tren » sach tren, lanh tren, sinh tren
tren cuoc » trong cuoc, tranh cuoc, tren co
khoa pho » khoa phu, khoa khoa, khoa phau
cach kho » bach khoa, cach thoi, cach pha
kho khan » khoa kham, khoa than
vu sach » vu bach, su sach, vu khach
sach va » sach xa, sach ha, sach dao
so sanh » do sanh

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( vu sach va thuc cach khoa pho thong ) or ( so sanh tren cuoc cach kho khan thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( vu sach va thuc cach khoa pho thong ) OR ( so sanh tren cuoc cach kho khan thong )).
• Adding a wildcard symbol may retrieve word variants: (( vu sach va thuc cach khoa pho thong ) or ( so sanh tren cuoc cach kho khan thong ))*.