Added these references to https://berthub.eu/articles/posts/on-long-term-software-development/#some-books https://berthub.eu/articles/posts/on-long-term-softwar

Added these references to https://berthub.eu/articles/posts/on-long-term-software-development/#some-books https://berthub.eu/articles/posts/on-long-term-software-deve..., thanks!