Some of the general reference works I have consulted include:
** The Encyclopedia Britannica .
I have read many articles from the Encyclopedia Britannica and from different editions , starting with the 1911 edition to the 2012 Ultimate Reference Suite electronic edition.
** Encyclopedia Universalis.
This is one of the most important French-language encyclopedias with in-depth articles about scientific subjects .
Of course there is also the newer online Wikipedia Encyclopedia , which has many good in-depth articles in many languages about various subjects.