Identifying the jurisdiction and time period the law report covers will help you identify the appropriate database to use.
In the following example,
Scruttons Ltd v Midland Silicones Ltd  AC 446
We discovered from the Cardiff Index that the ‘AC’ refers to the ‘Law Reports, Appeal Cases’ and it is a UK law report that started from 1891.
Looking at the mind map below, we see that for UK cases after 1865, we can use a variety of law databases such as , and BAILII (a free internet site).
In addition, the library also has hard copies of the English law reports.
On the other hand if we were looking for an English case reported before 1865, the mind map shows us that only and CommonLII provides access to these cases.