It may never win a Nobel Prize, but a 1951 paper describing a way to detect protein levels in a solution tops a new list of the 100 most cited research papers.

Fifty years ago, the American scientist Eugene Garfield started the Science Citation Index, the first organized effort to track citations in scientific literature. To mark the anniversary, the journal Nature asked Thomson Reuters, which now owns the index, to list the 100 most highly cited papers.

Neither Einstein’s papers on relativity nor Watson and Crick’s discovery of DNA’s double-helix structure made the cut. Instead, the list is dominated by papers describing methods or software that have become essential in their field. The top three papers are biochemical techniques for quantifying the amount of protein in a solution.

While oft-cited papers are certainly influential, said Richard Van Noorden, a co-author of the Nature article, being highly cited may have more to do with the “vagaries of citation practice” than scientific effect.