This is ten-page academic paper by two agricultural engineering professors that explore the Oregano herb species with special focus on zaatar or the hyssop plant described in the Bible, or “ezov” in Hebrew.
The main question they explore and answer is whether the biblical hyssop is same as the zaatar herb of our time. While doing so, they present an educational survey of the variety and classification of the oregano and zaatar species. While it is a scientific study, it is readable and aimed for the non scientist audience that want to make the connection of present day zaatar and hyssop from thousands of years ago.
The paper really offers an appreciation of the differences in the zaatar herb depending on where it is planted or found in the wild. They sample 22 different zaatar herbs and only from a relatively small geography of the Holy Lands and show the differences in quantity and type essential oil content (which drives flavor), mainly between thymol and carvacrol.
We like to refer to academic research like this paper to show that real zaatar herb is a series subject, and that most zaatar mixes on market have little to no real zaatar in them, and we are not exaggerating when we say that most zaatar claims sold on market have ground straw with other spices and fillers and no real zaatar herb.
Here is full reference and link:
Fleisher, Alexander, and Zhenia Fleisher. Identification of biblical hyssop and origin of the traditional oregano-group herbs in Mediterranean region Economic Botany, vol. 42, no. 2, 1988, pp. 232–241.