Following weeks of pressure, Amazon has pulled a number of so-called "conversion therapy" books by Dr. Joseph Nicolosi, a proponent of the debunked theory that one can change their sexual orientation or gender identity. However, a number of books by other authors pushing the dangerous practice remain on the company's virtual bookshelves, as well as those of its competitors.

UK-based activist Rojo Alan became aware of Nicolosi, who died in 2017, after a local church planned a screening of a pro-conversion therapy film, which ended up being cancelled due to backlash.

"I was shocked that this was actually happening in my town, so I started Googling about it, which led me to Joseph Nicolosi's website and then to his books that were [on] sale on Amazon and Wordery," Alan told Business Insider.

In particular, Alan, who was subjected to conversion therapy himself as a child, pointed to the book A Parent's Guide to Preventing Homosexuality as troubling. Wordery responded within 24 hours, pulling Nicolosi's books. It took Amazon three weeks to follow suit.

Meanwhile, a number of other titles by different writers pushing the same, or a similar, message remain for sale on both Amazon and Wordery, as well as through Barnes & Noble, which is also still selling Nicolosi's books.

Some of the titles still available through the online retailers include Help! My Teen Struggles with Same-Sex Attractions, by Ben Marshall, and Same-Sex Attraction: A Parents' Guide, edited by John F. Harvey and Gerard V. Bradley.

Amazon confirmed to NewNowNext that some titles had been removed, noting while it offers a variety of viewpoints to customers, it retains the right to pull material based on its content guidelines.

Those guidelines include prohibiting products containing "violent or offensive material that has no historical significance," as well as those that "promote intolerance based on race, religion, and sexual orientation."

"There’s quite a few that exist and I am still going to pursue this," Alan tells NewNowNext. An online petition asking Amazon to pull all such titles has gathered over 80,000 signatures.

Conversion therapy on minors has been banned in 18 states, as well as the District of Columbia and Puerto Rico. Last year, the British government announced it would ban the practice as part of its LGBT Action Plan.

NewNowNext has reached out to Wordery and Barnes & Noble as well and this article will be updated if we receive a response from either, or both.

UPDATE: A spokesperson for Wordery provided the following statement to NewNowNext:

We are currently investigating this and will endeavour to identify and remove any item(s) of this nature that could cause offence. We have a catalogue of 18 million titles, so it’d be impossible for us to hand-select or check every single title we sell; therefore, very occasionally, inappropriate or unvetted items can slip through unnoticed. Whilst we believe in freedom of speech; we do not tolerate anything that implies or incites intolerance or hatred in any context.

Wordery has pulled the remaining conversion therapy books, and searching for the term "same-sex attraction" (or the variant "same sex attraction") on Wordery no longer brings up any results, as seen below.

However, those same books are still available for purchase through Amazon, as well as Barnes & Noble.