can't open file epub create on android

[hoanhtranh90]

i can't open book from android, when i validate this epub return some error

ERROR(RSC-005): ./books/Bo/databases/eBookIt/temp_uploads/1623396317.epub/OEBPS/content.opf(25,16): Error while parsing file: element "opf:guide" incomplete; missing required element "opf:reference"