I do have a list of places to use for searching, but I almost always find such specific search engines to actually be missing most of the findings I make, specially because they apparently only deal with text, not other forms of scientific resource.
So, instead I suggest you to search on normal search engine and when you find something interesting, do a basic reputation/background check on who the author of such content is. If such person has at least one true academic publication (only counting text in this case) in another place (if he's writting in his own blog, or group blog, or if it's an audio/video content) or in another issue or edition of the same journal, then his article can **probably** be used as a reference. To give you an idea, most of the good publications about the importance of free/libre software movement/philosophy/actvism I have found aren't in the academic search engines I have right now, and I'm not talking about GNU.org, nor FSF.org, nor SFLW's website, nor FaiF.us, nor the FSF sister organization's websites, nor Copyleft.org, nor SFConservancy's website. Interestingly enough, some of these publications don't have proper license, so this leaves a big question mark until I get the time to contact the authors and ask which license the publication is under. If you do insist on a list of academic search engines, though, here's mine (most of then aren't search engines, but libraries. Besides, most of the academic search engines existing in the world come with an onus: requirement to run non-free software, through a way which you probably have heard about, that is, JavaScript, but the language doesn't matter, it would still be an issue with other language): http://www12.senado.gov.br/institucional/biblioteca http://framabook.org/ http://framabookin.org/ http://www.dominiopublico.gov.br/pesquisa/PesquisaObraForm.jsp http://scielo.br/ https://framabee.org/ https://www.gutenberg.org/
