Question: Who is the author of the novel that had a movie based on it and contained the song "Thodi Der"?

full_context: Document 1: Rab Ne Bana Di Jodi: Rab Ne Bana Di Jodi (English: "A Match Made By God") is a 2008 Indian romantic comedy film written and directed by Aditya Chopra and produced by Yash Chopra and Aditya Chopra under the banner Yash Raj Films. The film is inspired by "The World of Apu" of legendary Bengali film maker Satyajit Ray. The film stars Shah Rukh Khan and Anushka Sharma in the lead roles. Khan plays a mild-mannered office worker named Surinder Sahni, whose love for the beautiful and vivacious Taani (Anushka Sharma) causes him to transform himself into the loud and fun-loving "Raj" to win her love. It was released worldwide on 12 December 2008 and marked Aditya Chopra's return to directing after an eight-year break, following his previous film, "Mohabbatein".
Document 2: Ladies vs Ricky Bahl: Ladies vs Ricky Bahl is a 2011 Indian romantic comedy film directed by Maneesh Sharma and produced by Aditya Chopra of Yash Raj Films. It stars Ranveer Singh opposite Anushka Sharma in lead roles along with Dipannita Sharma, Aditi Sharma and debutant Parineeti Chopra. Ranveer plays a conman named Ricky Bahl who cons women until three of these women unite to con him back. The story was inspired by Jeffrey Archer's novel "Not a Penny More, Not a Penny Less" and the Hollywood comedy "John Tucker Must Die". It was released on 9 December 2011 to a mixed response from critics but eventually ended up being a commercial success, earning ₹84 crores gross from the box office on a budget of ₹20 crores.
Document 3: I Hate Luv Storys: I Hate Luv Storys is a 2010 Indian romantic comedy drama film starring Sonam Kapoor and Imran Khan in the lead roles. It is written and directed by Punit Malhotra and produced under Karan Johar's Dharma Productions and Ronnie Screwvala's UTV Motion Pictures. The film was released on 2 July 2010 and went on to become a box office hit. "I Hate Luv Storys" was partly filmed in Queenstown, New Zealand.
Document 4: Half Girlfriend: Half Girlfriend is an Indian English coming of age, young adult romance novel by Indian author Chetan Bhagat. The novel, set in rural Bihar, New Delhi, Patna, and New York, is the story of a Bihari boy in quest of winning over the girl he loves. This is Bhagat's sixth novel which was released on 1 October 2014 by Rupa Publications. The novel has also been published in Hindi and Gujarati versions as well. A Hindi film adaptation released on 19 May 2017.
Document 5: Main Rahoon Ya Na Rahoon: "Main Rahoon Ya Na Rahoon" is a 2015 song by Indian recording artist Armaan Malik composed by Amaal Mallik. The accompanying music video has been shot in Goa, India and features Bollywood actors Emraan Hashmi and Esha Gupta. It was released on YouTube by T-Series on 23 November 2015. The song has been well received crossing over 80 million views as of 23rd May 2017.
Document 6: Phir Bhi Tumko Chaahunga: "Phir Bhi Tumko Chaahunga" (English: "I will still love you") is a song from the Indian film "Half Girlfriend". Picturised on Shraddha Kapoor and Arjun Kapoor, the song has been sung by Arijit Singh and Shashaa Tirupati. The music of the song is composed by Mithoon and the lyrics are penned by Manoj Muntashir. Reprise version of the track is sung by Arijit Singh titled, "Pal Bhar (Chaahunga Reprise)", and also another version titled, "Phir Bhi Tumko Chaahungi" is sung by Shraddha Kapoor along with the instrumental "Half Girlfriend (Love Theme)".
Document 7: Ali Zafar: Ali Mohammad Zafar (born 18 May 1980) is a Pakistani singer-songwriter, model, actor and painter. Zafar started out on Pakistani TV before becoming a popular musician. He then also established a career in Hindi cinema and his success led many Pakistani actors to venture into Hindi films. He has received five Lux Style Awards and a Filmfare Award nomination.
Document 8: Siddharth Mahadevan: Siddharth Mahadevan is an Indian playback singer and composer who is known for his songs in the film "Bhaag Milkha Bhaag" in which he sang "Zinda" and the rock version of the title song "Bhaag Milkha Bhaag". He got further acclaim for the song Malang by music director Pritam in the movie Dhoom 3. He has also composed music for the Marathi film "Swapna Tujhe ni Majhe" with his cousin Soumil. he also composed all the songs of a Marathi movie sugar salt ani prem with his cousin Soumil Shringarpure
Document 9: Nakash Aziz: Nakash Aziz (born February 24, 1985), also known as Nakash, is an Indian playback singer and music composer. He has assisted the legendary composer A. R. Rahman on films like "Highway", "Raanjhanaa", "Rockstar", "Delhi 6" and "I" in Hindi. He is popularly known for playback of songs like "Jabra Fan" from "Fan",<ref name="http://www.deccanchronicle.com/ 2016"> </ref> "Sari Ke Fall Sa" and "Gandi Baat" from the film "R... Rajkumar" (2013) and "Dhating Nach" from film "Phata Poster Nikhla Hero" (2013); the latter two films of which were picturized on Shahid Kapoor.
Document 10: Half Girlfriend (film): Half Girlfriend is an Indian romantic drama film based on the novel of the same name written by Chetan Bhagat. The film is directed by Mohit Suri and features Arjun Kapoor and Shraddha Kapoor in the lead roles.
Document 11: Zindagi Tere Naam: Zindagi Tere Naam is a 2012 Hindi-language Indian feature film directed by Ashu Trikha, starring Mithun Chakraborty and Ranjeeta in lead roles and the film is a matured love story. The film was completed in 2008, but released only in 2012 with limited prints. The film is based on the American Nicholas Sparks' novel "The Notebook" and the 2004 movie of the same name.
Document 12: 2 States (film): 2 States is a 2014 Indian romantic drama film co written and directed by Abhishek Varman based on the 2009 novel of the same name written by Chetan Bhagat. It is produced by Karan Johar and Sajid Nadiadwala. The film stars Arjun Kapoor and Alia Bhatt in lead roles. The film was released on 18 April 2014.
Document 13: Thodi Der: "Thodi Der" (English dub: Stay a Little Longer) is a popular song from the soundtrack of the Bollywood film Half Girlfriend. The song was composed by Pakistani singer Farhan Saeed, who originally performed the song (titled "Tu Thodi Dair")) with established Indian singer Shreya Ghoshal.
Document 14: Sahir Ali Bagga: Sahir Ali Bagga (Urdu: ساحر علی بگا‎ ) is a Pakistani singer, music director and composer from Lahore, who composes music for Lollywood and other independent singers. Recently he has composed music for the Pakistani movie, "Zinda Bhaag (2013)". He also worked on the soundtrack of Pakistani movies, "Hijrat" and "Tamanna", contributing two songs to the latter; Koi Dil Mein and Chell Oi. He has also composed music of Hum TV's Ishq-e-Benaam.
Document 15: Aashiqui 2 (soundtrack): Aashiqui 2 is the soundtrack to the 2013 Bollywood romance film of the same name, directed by Mohit Suri and starring Aditya Roy Kapoor and Shraddha Kapoor in the lead roles. The album was produced by Bhushan Kumar and Mahesh Bhatt under the banner T-Series and Vishesh Films. the songs of the film were mostly composed by Jeet Gannguli, although Mithoon and Ankit Tiwari composed two songs each (including both versions) as guest composers. Irshad Kamil wrote lyrics for most of songs on the album. Sandeep Nath wrote both versions of "Sunn Raha Hai", while Mithoon wrote "Tum Hi Ho" and Sanjay Masoom wrote "Bhula Dena". Arijit Singh sang six of the songs on the album. The music became very popular after its release on 8 April 2013, with songs "Tum Hi Ho" and "Sunn Raha Hai" topping the charts across various platforms in India. Jeet Gannguli reused the tune from his own Bengali composition "Mon Hariye Beghorey" for "Milne Hai Mujhse Aayi".
ground_truth: Chetan Bhagat