Write queries in XQuery on the bibliography DTD fragment as shown below to do the following.

a. Find all authors who have authored a book and an article in the same year.

b. Display books and articles sorted by year.

c. Display books with more than one author.

<!DOCTYPE bibliography [

<!ELEMENT book (title, author+, year, publisher, place?)>

<!ELEMENT article (title, author+, journal, year, number, volume, pages?)>

<!ELEMENT author ( last-name, first-name) >

<!ELEMENT title ( #PCDATA )>

· · · similar PCDATA declarations for year, publisher, place, journal, year,

number, volume, pages, last-name and first-name

] >