Amazon is no longer selling books by a Catholic author who promoted the scientifically discredited idea that it’s possible to alter a person’s sexual orientation through conversion therapy.

Several titles by psychologist Dr. Joseph Nicolosi were removed from the online retail giant’s website, Amazon confirmed to HuffPost in an email Friday. A search for Nicolosi’s books on the site failed to produce any results. The company said it reserves the right to not sell books that contradict its content guidelines.

LGBTQ activists have been urging Amazon to take action against the books for months. More than 82,000 people have signed a Change.org petition since it launched five months ago, calling on the company to stop selling books that promote conversion therapy.

Sam Brinton, head of advocacy and government affairs for the suicide prevention group The Trevor Project, said they consider the removal of Nicolosi’s books to be a positive step.

“Amazon is the nation’s largest seller of online books,” Brinton said. “It is significant that they are taking the threat of conversion therapy seriously by refusing to be a party to the exploitation of concerned parents and other customers who deserve accurate information, not DIY conversion therapy manuals that should clearly be labeled as ‘fiction.’”

Nicolosi, who died in 2017, was known to some as the “father of conversion therapy,” sometimes called reparative therapy. This form of therapy operates under the premise that same-sex relationships are unhealthy ― a stance that the American Psychiatric Association repudiated in 1973, when it removed homosexuality from its list of mental illnesses.

Through numerous mediaappearances, Nicolosi promoted the idea that homosexuality is a symptom of early childhood trauma, and that people could diminish same-sex attractions through reparative therapy. He wrote several books outlining ways to supposedly cure queer people, including “A Parent’s Guide to Preventing Homosexuality” and “Healing Homosexuality: Case Stories of Reparative Therapy.”