Nephrite as a surface treatment. A lot of nephrite tools and amulets are known since the Early Neolithic (VII mill. BC) to the Late Chalcolithic (V mill. BC) on the Balkans (mainly Bulgaria; also in Greece, Serbia, Croatia) from two or more unknown sources - Balkan "nephrite culture". Such tools are found in the Later Neolithic of Poland (from the most probable local source Jordanów), Sardinia (Italy) (unknown source) and Switzerland (Kostov, 2005; 2013). Single or just a few finds of nephrite artifacts are reported also from some other European countries. During Neolithic times, the key known sources of nephrite jade
Tensor product of quadratic forms from this that if we have diagonalizations of our quadratic forms (which is always possible if formula_9 is invertible) such that then the tensor product has diagonalization Tensor product of quadratic forms The tensor product of quadratic forms is most easily understood when one views the quadratic forms as "quadratic spaces". If "R" is a commutative ring where "2" is invertible, and if formula_1 and formula_2 are two quadratic spaces over "R", then their tensor product formula_3 is the quadratic space whose underlying "R"-module is the tensor product formula_4 of "R"-modules and whose quadratic form is the quadratic form associated