Intro text referencing items[^1] and others[^2].

Extra context linking to third[^3].

[^1]: rayon-rs/rayon - Data parallelism library.
      <https://github.com/rayon-rs/rayon>

[^2]: Parallel Processing in Rust article.
      <https://kartik.example/parallel>

[^3]: Research paper overview with summary.
      <https://example.com/paper>
