wherein {TAIL ~ the first condition} that requires a larger storage capacity of the storage unit in the document reading is a reading condition where a difference is larger than an enough storage capacity to implement the functions other than {HEAD ~ the image reading function}, which difference is a storage capacity difference between: 
wherein { TAIL ~ the first condition } that requires a larger storage capacity of the storage unit in the document reading is a reading condition where a difference is larger than an enough storage capacity to implement the functions other than { HEAD ~ the image reading function } , which difference is a storage capacity difference between :
OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH