private abstract class Citation {

        private Person[] authors;
        private String title;
        private int year;

        public Citation(Person[] authors, String title, int year) {
            this.authors = authors;
            this.title = title;
            this.year = year;
        }

        public Person[] getAuthors() {
            return authors;
        }

        public String getTitle() {
            return title;
        }

        public int getYear() {
            return year;
        }

        public abstract int getPagesCount();
    }


    private class Book extends Citation {

        private String publisher;

        private String address;

        private int pagesCount;

        public Book(Person[] author, String title, int year, String publisher, String address, int pagesCount) {
            super(author, title, year);
            this.publisher = publisher;
            this.address = address;
            this.pagesCount = pagesCount;
        }

        @Override
        public int getPagesCount() {
            return pagesCount;
        }
    }


    private class InCollection extends Book {

        private String bookTitle;

        private Person[] editors;

        private int startPage;

        private int endPage;

        public InCollection(Person[] author, String title, int year, String publisher, String address, String bookTitle, Person[] editors, int startPage, int endPage) {
            super(author, title, year, publisher, address, endPage - startPage);
            this.bookTitle = bookTitle;
            this.editors = editors;
            this.startPage = startPage;
            this.endPage = endPage;

        }

        public String getBookTitle() {
            return bookTitle;
        }

        public Person[] getEditors() {
            return editors;
        }

        public int getStartPage() {
            return startPage;
        }

        public int getEndPage() {
            return endPage;
        }
    }


    private class Person {

        String name;

        String surname;

        public Person(String name, String surname) {
            this.name = name;
            this.surname = surname;
        }

        public String getName() {
            return name;
        }

        public String getSurname() {
            return surname;
        }
    }