In a related issue, an attempt to obtain an article beginning on page 415 of a scientific journal revealed that the online version, available via Science Direct, only shows articles in that volume up to page 389. The response to a query to Science Direct was that at least 2% of its electronic journal content is missing. [1]
[1] Warner, Dorothy and Buschman, John. Studying the Reader/Researcher Without the Artifact: Digital Problems in the Future History of Books. Library Philosophy and Practice Vol. 7, No. 1 (Fall 2004) http://www.webpages.uidaho.edu/~mbolin/warner-buschman.htm