Hmm, please humor me then, what subject were these books on? Not the title, but the subject? Was it numerical analysis and approximation theory? What kind of people wrote them? What was their profession? Did you say they were mathematicians? Also, what country were they from? Please post the bibliography. I might now what's going on here.
Also, google links to scientific publications. Don't dis a good google search. Try it.
First, a good google search is using google scholar. It's good on it's own, but if you have a university library that is synched up with it than you can log into various databases that google knows you have access to (it's not always right, but it definitely simplifies things).
As for the books.
Numerical analysis is a subject. Traditionally, Analysis (of which Numerical analysis is a branch) is one of the few main mathematical sciences, although the distinctions are so lost at this point that I don't even recall what they are. However, calculus is the first step in analysis (I believe that in addition to analysis, the other disciplines included geometry and algebra, but I recall there being four...). Thanks to several centuries from Newton onwards, we've moved passed Riemann integrals into measure theory (although the former is still taught for needless reasons). Lebesque integrals, topology, and measure theory are the bulk of analysis. Numerical analysis is now an umbrella category under which various separate but related approximation methods for different kinds of problems fall. Both the reals and the rational numbers (a subset of the reals) are dense, but the former is infinitely more dense and is uncountable. Which means that precision becomes extremely important as the limiting process, despite significant achievements, is still idealized. In order for a computing device to carry it out, it requires some sort of approximation. Numerical analysis covers the various ways in which this is done for different types of issue.
As for the bibliographies (in no particular order):
Stoer, J., & Bulirsch, R. (2002).
Introduction to numerical analysis (Vol. 12). Springer.
Kress, R. (1998).
Numerical analysis (Graduate Texts in Mathematics, vol. 181).
Burden, R. L., & Fsires, J. D. (2011).
Numerical Analysis. Brooks/Cole, Cengage Learning.
Zarowski, C. J. (2004).
An introduction to numerical analysis for electrical and computer engineers. Wiley-Interscience.
Stepanets, A. I. (2005).
Methods of approximation theory. De Gruyter Mouton
Katō, T. (1995).
Perturbation theory for linear operators (Vol. 132). Springer Verlag
Conte, S. D., & Boor, C. W. D. (1980).
Elementary numerical analysis: an algorithmic approach. McGraw-Hill Higher Education
Atkinson, K. E., & Han, W. (2009).
Theoretical numerical analysis: a functional analysis framework (Vol. 39). Springer
There are a few more I know I have someone (one on ordinary differential equations and the other on partial), but I hope this list can at least give you enough to malign my credibility again. Let me know if you'd like other sources that I should trade in for a google search.