One Direction's Harry Styles has been writing songs under the name Mick Greenberg. Whether those songs are about Taylor Swift is for you to decide. We pieced together the proof that Styles and Greenberg are one and the same, but first let's back up.

Directioners Catch On

Rumors first started that Styles and Greenberg might be the same person last year, when pop duo Alex & Sierra revealed that a guy named Mick Greenberg had co-written the song "I Love You," off their debut album, It's About Us. Directioners immediately connected that with Harry, who once told BBC Radio he checked into a hotel as "Mick Green."

Though the song appears on Alex & Sierra's album, "I Love You" has obvious references to Styles' ex, Swift, including what seem to be lyrical responses to her song "I Knew You Were Trouble" and a hint to her favorite number, 13. But to this day, when the romantically involved musical duo are asked about Harry, they just giggle and suggest that Mick Greenberg is Shaquille O'Neal. Mick would be a great pseudonym for Styles, because of Harry's Mick Jagger-like tendencies.

Mick Greenberg's Catalog

Clearer answers are found on the ASCAP website, where they list legal songwriting credits. And what do you know? When you do a search for Mick Greenberg and click on any of his songwriting credits -- including "I Love You" -- you're automatically directed to the name Harry Styles.

Harry's side-hustle as a songwriter is an open secret because ASCAP's information is easily available to the public. (MTV News reached out to ASCAP and reps for One Direction but had not heard back at press time.)

A whole treasure trove of songs come up under Harry's name -- 35 to be exact. The same 35 songs show up under Mick Greenberg's name too. Of those songs, 13 of them are One Direction songs, 3 are performed by other people and 19 are listed without performers.

Of course, there's the Alex & Sierra song we mentioned, but the results also reveal that Styles/Greenberg has written for Ariana Grande and Gavin Degraw.

Back in July, Grande dished on their collaboration during MTV's "Total Ariana Live": "I was at the studio one day and [Harry] was there, and literally, [songwriters] Johan [Carlsson] and Savan [Kotecha] were like, 'Hey, do you want to write something for Ariana?' And he was like, 'Sure, mate.' And he just did."

Degraw's collaboration with Harry, "Not Our Fault," was written for DeGraw's greatest hits album released in October (but did not make the final cut). Meanwhile, Grande's My Everything saw its release in August. This proves that Harry has been writing at least since summer 2014.

So what are these 19 other songs listed without performers? There's definitely enough to put them all on an album, but we'll leave you to your own conclusions about that. The song "I Fell In Love With A Beautiful Girl" is co-written with Carlsson. The other 18 tracks are co-written with Augustana singer Dan Layus:

>> "Better Than Being Alone" - written with Dan Layus

>> "California" - w/ Layus

>> "Can't Get Enough" - w/ Layus

>> "Fall Apart" - w/ Layus

>> "Fun For Now" - w/ Layus (and 1D producer Julian Bunetta)

>> "Have And Hold" - w/ Layus

>> "I Just Wanna Be Your Man" - w/ Layus

>> "Kiss It Better" - w/ Layus

>> "Kiss Me" - w/ Layus

>> "Kissed You In The Rain" - w/ Layus

>> "Like Everybody Else" - w/ Layus

>> "Like You Do" - w/ Layus

>> "Love You Like You're Leaving" - w/ Layus

>> "Might Not Want You" - w/ Layus

>> "One Desire" - w/ Layus

>> "One Of Those Nights" - w/ Layus

>> "Second Chance" - w/ Layus

>> "You Still Have My Heart (Even If You Don't De" - w/ Layus

The last song title is cut off, but Directioners believe the missing words to be "Deserve It."

Those Pesky One Direction Breakup Rumors Again

In late 2013, rumors spread that Styles was recording without One Direction, causing many to believe he might want to go solo. A rep for the band was quick to make this statement: "The boys sometimes work up ideas separately as well as working together, as they did last year."

By contract, One Direction are reportedly required to release one more album with Simon Cowell's Syco label -- their fifth -- along with a greatest hits collection.

In an interview with Barbara Walters in 2012, the boys denied any future separation. "No way. It's not even, like, a question," Zayn Malik said. "We'd just be like, 'No, I’m not doing it.'" However, that was three years ago. People change.

Solo or not, you have to admit, that's a lot of Harry Styles songs that we haven't heard, and we're hoping Harry, Mick Greenberg -- or anyone -- will record and release them soon!

Where do you think these Harry Styles songs will end up? Share your guesses in the comments.

[Correction: An earlier version of this article incorrectly stated that "Not Our Fault" was included on Gavin DeGraw's greatest hits album. Sorry!]