public ReadingRecordByPage(ReadingRecordByBook firstBookRecord, string bookName) : this(firstBookRecord.Date, firstBookRecord.ReadPage, bookName) { }
public ReadingRecordByPage(ReadingRecordByBook bookRecord1, ReadingRecordByBook bookRecord2, string bookName) : this(bookRecord2.Date, bookRecord2.ReadPage - bookRecord1.ReadPage, bookName) { }