: A pack containing 200+ high-res paper elements for digital design.

There is no specific academic "solid paper" titled or primarily about "." This phrase appears to be a promotional tagline or a file name associated with digital downloads rather than a scholarly subject.

: A systematic review on quantifying "quality" through subjective and objective perception metrics.

If you meant "solid paper" in the literal engineering sense, these peer-reviewed sources are highly cited:

If you are searching for a (often found in ZIP files for design), popular commercial options include:

: Industry-standard definitions from MarketMuse regarding what makes content valuable, relevant, and engaging to an audience. On "Solid" Materials (Materials Science)

: A comprehensive textbook review covering metals, ceramics, and polymers.