On March 28th, the New York Times will begin charging all but the most infrequent users to read articles online. In a letter to readers, Arthur Sulzberger, Jr., the publisher of the paper, laid out the details of the paywall, which he said will go into effect immediately in Canada and on March 28th for the rest of the world. He called the move "an important step that we hope you will see as an investment in the Times, one that will strengthen our ability to provide high-quality journalism to readers around the world and on any platform." Sulzberger said that readers will be able to read 20 articles per month at no charge. Once they click on the 21st piece, however, they'll be presented with three payment options: $ 15 for four weeks of online and mobile application access, $ 20 for access to the site and the iPad application, or $ 35 for access to everything. People who already receive the printed paper through home delivery will enjoy free and unlimited access to the Times on all platforms. These details largely agree with earlier reports on how the paywall would work. The Times had made it clear that it did not want to imitate the total paywalls put into effect by papers such as The Times of London and Newsday, which block access to all contents unless the reader pays. The paper also signaled that it wants to stay relevant in the social media world. According to Sulzberger's announcement, people who come to the Times site from Facebook, Twitter or from blogs will be able to read those articles even if they have gone over their monthly limit. However, Sulzberger said that a limit will be placed on "some search engines", meaning that after readers have accessed a certain number of articles from search engines, any further articles they access from there will be added to their monthly count. It was reported that the only search engine that will be affected this way is Google, where there will be a five-article limit. This marks a clear attempt by the Times to close what could be a giant loophole  , since so much online traffic is directed through Google. But it also presents a risk for the Times for the same reason. Sulzberger seems well aware of the risk. "The challenge now is to put a price on our work without walling ourselves off from the global network," he said, adding that the Times must "continue to engage with the widest possible audience." The author's main purpose in the text is to   _  .
describe research findings report a piece of news make advertisements suggest a solution