Hey, I'm unsure whether this belongs here but I'll give it a shot. I'm writing a 10 page paper on prog rock from the 60s to the 70s. Does anyone know any good books/online articles that would make good sources? Thanks alot.
to be honest, I wouldn't exactly identify art rock and prog rock as being the same, even though the line between the two is often times blurred.

for instance, consider Pink Floyd back in the 60's - their psychedelia laced sound was more leaning towards "art rock" than progressive music. Later on in the 70s with Roger Water's taking a greater hand in the musical direction of the band, they leaned towards concept oriented albums like DSOTM and "The Wall", and also in terms of their music which leaned towards more grandiose arrangements. I mean even Deep Purple's earlier albums can be said to have progressive elements.

The same problem arises when trying to understand Frank Zappa's music. The lyrical and conceptual ideas in the song lean more towards abstract or even absurd artistic expression while the music varies between experimental and even avant-garde, or towards a sound more grounded in hard rock with progressive elements.

To turn it around, consider a band like the Talking Heads that started off as essentially a punk band. But soon they added more orchestration to their sound, along with sophisticated pop hooks and clever melodies. Furthermore the addition of musicians like Bernie Worrell on keyboards and Adrian Belew on guitar further cemented their art rock tendencies.

I mean one could consider the Doors as an art rock band, because they blended rock n' roll with jazz and blues in a psychedelic framework interpreted live as modern theater.

Since you are writing a 10 page paper, you could build a viable thesis which explores the nuances of similarities and differences between psychedelic music, art rock and progressive music - especially in context of the socio-cultural scene at that time.

For straight up progressive music from the 60s and 70s, you could look at bands which are traditionally labeled as prog rock acts like Yes, Rush, ELP and King Crimson. **** you could write a 10 page paper alone on King Crimson!