I think in the Soviet bloc, "higher mathematics" referred to mathematics taught at higher institutions (i.e. universities or technical institutions at the same

I think in the Soviet bloc, "higher mathematics" referred to mathematics taught at higher institutions (i.e. universities or technical institutions at the same level). This usage is a bit different from that in the Commonwealth of Nations (see https://en.wikipedia.org/wiki/Further_Mathematics https://en.wikipedia.org/wiki/Further_Mathematics for instance). As for the current text, while it does mostly cover high-school calculus, some portions of it (e.g. contour integration, analytic functions and Dirac delta function) are definitely outside high-school curricula. As the authors indicated in the preface, the intended audience of this book include high-school students, high-school teachers and first-year college students.