(CNN) - Renowned physicist Stephen Hawking was days from death, but that didn't stop him working.
Now his colleagues at Cambridge and Harvard universities have released what may be his final research paper.
Entitled "Black Hole Entropy and Soft Hair," it considers the so-called black hole information paradox, a puzzle that Hawking devoted much of his working life to researching.
Hawking and his collaborators sought to explain what happens to the information contained in particles that are pulled into a black hole if that black hole then ceases to exist.
If a particle's information also disappeared, this would stand counter to quantum theory -- that nothing is truly ever lost.
The paper was completed in the days before Hawking's death in March at age 76, physicist Malcolm Perry -- its co-author along with Andrew Strominger and Sasha Haco -- wrote in Britain's Guardian newspaper.
It outlines further findings on "soft hair," a term coined to describe some of the particle's information that may be left around the black hole's event horizon -- the point at which nothing can be seen and nothing can escape.
"In 2016, Stephen, Andy and I found that black holes have an infinite collection of what we call 'soft hair.' This discovery allows us to question the idea that black holes lead to a breakdown in the laws of physics," wrote Perry, a professor of theoretical physics at the University of Cambridge, in The Guardian.
"Stephen kept working with us up to the end of his life, and we have now published a paper that describes our current thoughts on the matter."
The paper includes a tribute to Hawking's work. "We are deeply saddened to lose our much-loved friend and collaborator Stephen Hawking whose contributions to black hole physics remained vitally stimulating to the very end," the authors wrote.
"This paper summarizes the status of our long-term project on large diffeomorphisms, soft hair and the quantum structure of black holes until the end of our time together."
Hawking's great achievements were remembered at a memorial service in June at London's Westminster Abbey, during which an antenna in Spain beamed his voice out into space, toward a black hole.
Another posthumously published paper, co-authored by Thomas Hertog at the University of Leuven in Belgium, re-examined the theoretical characteristics of the Big Bang using new mathematical applications. Its final version was submitted just 10 days before Hawking died.
Hawking also published hugely popular books that allowed readers to join him in probing the mysteries of the universe. His landmark "A Brief History of Time" sold more than 10 million copies.
In 1963, shortly before his 21st birthday, he was diagnosed with amyotrophic lateral sclerosis, a neuro-degenerative disease, and although he required a wheelchair and a speech synthesizer, Hawking lived for many years beyond the initial prognosis.