The battle over Google's effort to digitise the world's books and create a vast online library has intensified¹.

谷歌试图将世界上的图书数字化并建立一座巨大的在线图书馆的意图加强。

One of Google's aims is to "bring the world's lost literature back to life"

Authors have until Friday to opt² out of（决定不参加，决定退出） the $125m settlement the search giant made with authors and publishers.

The date for comments to the New York court overseeing the class action suit was extended from Friday to Tuesday, after the filing system went down.

As time ticks away, supporters and critics have been manning both sides of the debate to win the public case.

'Civil right'

The settlement reached last October stemmed from a 2005 legal suit that Google faced for scanning out-of-print works without explicit³（明确的，详述的） permission（同意，许可） from rights holders⁴.

If approved by a judge, Google would create a Book Rights Registry where authors and publishers could register works and be compensated⁵.

Ahead of Friday's opt-out for authors, Google lined up a number of professors, students and civil rights activists⁶ who support the deal.

"We see access to knowledge as a civil right," Wade⁷ Henderson, president and chief executive of the Leadership Conference on Civil Rights, told reporters in a conference call.

"Information enables individuals to learn, to create and to pursue their dreams. Access to knowledge defines the meaning of equal opportunity in a democratic society," said Mr Henderson.

Access was also the issue that led the United States Student Association to throw its weight behind the Google books programme.

"Today, millions of books are accessible only to the privileged（有特权的） few who are accepted to universities and can actually afford to attend," said association president Gregory Cendana.

"With Google books, any student anywhere in the US will have the books in the greatest libraries of the world at their fingertips."