I wrote a while back on the legacy of Bill Spicer, a name that you may not have heard, but whose influence probably have affected your life in some way. One of such ways is the scenario where there are just some papers, no matter how old they are, that continue to be used, cited, and scrutinized. These papers continue to be highly relevant even today.
One such paper is this one, published in 1993, and written by Spicer and Herrera-Gomez. It deals with the physics of photocathodes. For those of us in the accelerator physics field, this paper continues to be cited and studied when we deal with photocathodes for particle accelerators. Other than Sommer's Photoemissive Material text, this paper is a tour de force in almost everyone one needs to know about basic photoemission (not angle-resolved or resonant etc.) processes that are relevant in a photoinjector.
As I've said before, this is roughly what Spicer started with when he delved into photoemission physics. It is fitting that, to this day, his work still has relevance in that field of study.