... properties, that will be used extensively to operate and simplify long expressions throughout this book. Since we extend and condense tensors very frequently, i .e. , we represent tensors as vectors ... from one of these representations to the other, and vice versa. These operators are used initially to solve some important matrix equa-tions that are introduced, together with some interesting ... vectors to take full advantage of vector theory and tools, and then we recover their initial tensor representation, we present the corresponding extension and condensation operators that permit...