Quetext has not specifically imbedded any 'offline' sources into its search index. However, most information that is available offline, has made its way online in some form or another, and thus has made it's way into our index. Furthermore, it is unlikely that an instance of plagiarism would go unnoticed by our software solely because it was plagiarized from an 'offline' source.
Quetext works most accurately on English texts. However, most Romanic languages that have a significant online presence will give very accurate results. Please note, that there are no translations performed by our software to check for plagiarism in other languages. For example, if you scan a document written in Spanish that contains a plagiarized sentence from an English source that was translated to Spanish, the software will not translate the phrase to English, it will search it as-is.
Quetext does not condsider common phrases plagiarism, even if we find a match for it. For example, if we find matching sources for the phrase "during our trip to the store we saw" we wouldn't consider that plagiarism because it is a very common idea/phrase. But we would consider a phrase like "a topological dimension of 1, but it is by no means a rectifiable curve: the length of the curve between any two points on the Koch Snowflake" to be possible plagiarism because it is very uncommon phrase and idea.
Most likely because we found a phrase in your document that happens to be similar enough to content elsewhere. This is where you must use your own discretion. When it finds a similar match, the similar text along with a link to the full text is provided, so that you can decide whether or not it is plagiarized.
Some people will test our software by scanning an entire page from Wikipedia, for example; and are confused when certain phrases don't show a match as 'plagiarism'. The reason for this is due to an intentional design decision in our algorithm. Quetext was built to work best with actual documents like a student's essay, a lawyer's terms of service, or a blogger's article, for example. What does that mean? It means that Quetext looks beyond the naïve verbatim search approach. Even if the software finds that a phrase has an exact match elsewhere, it will go even further to check the likelihood that the text was actually plagiarized. We utilize a proprietary machine-learning algorithm that considers many factors, in order to give you the most useful and accurate results.