Calculus  
This short introductory text focuses mainly on integration and differentiation of functions of a single variable, although iterated integrals are discussed. 
The Data Analysis BriefBook  
This BriefBook is a much extended glossary or a much condensed handbook, depending on the way one looks at it. In encyclopedic format, it covers subjects in statistics, computing, analysis, and related fields, resulting in a book that is both an introduction and a reference for scientists and engineers, especially experimental physicists dealing with data analysis. 
Graphentheorie  
The German edition of this free standard textbook of modern graph theory has been carefully revised, updated, and substantially extended. Covering all its major recent developments it can be used both as a reliable textbook for an introductory course and as a graduate text: on each topic it covers all the basic material in full detail, and adds one or two deeper results to illustrate the more advanced methods of that field. 
Elementary Calculus: An Approach Using Infinitesimals  
This is a calculus textbook at the college Freshman level based on Abraham Robinson's infinitesimals, which date from 1960. Robinson's modern infinitesimal approach puts the intuitive ideas of the founders of the calculus on a mathematically sound footing, and is easier for beginners to understand than the more common approach via limits. 
Calculus for Beginners and Artists  
Topics covered in this free online book include: Why Study Calculus?, Numbers, Linear Functions, Quadratics and Derivatives of Functions, Rational Functions and the Calculation of Derivatives, Exponential Functions, Substitution and the Chain Rule, Trigonometric Functions and their Derivatives, Inverse Functions and their Derivatives, Numerical Differentiation, and NonDifferentiable Functions, Review of Functions and Derivatives, Modeling Applications to Physics and etc. 
