Each database has a scope document, which may advise details such as: coverage (currency), list of citation abbreviations, sources.
They are especially useful for databases that cover many sources (large range of Journals or Reports). For example the database called All United Kingdom Reports covers many reports. The scope for this database will show which reports for example:
* Fleet Street Reports series, published by Sweet & Maxwell from 1966 to present.
* The Law Reports series, published by Incorporated Council of Law Reporting For England & Wales.
* Queens Bench from (1891) 1 Q.B. to 1901 1st vol. and 1952 2nd vol. to present.
Note: this is only listing a few, there are many more.