CCH Intelliconnect  includes many resources for researchers.

To limit research to Federal tax, change the practice area settings to Federal Taxes, and select apply.

Results are now limited to Federal Taxes.  Researchers may browse the content, or select Citator, to locate cases, rulings, tax code sections by known citations.

• In addition to selecting Citator to search by known citations, Search Options enables one to build keyword searches by adding synonyms and by building searches using additional connectors that help focus results, such as phrase searches, or searching for words in the same sentence or paragraph or within a given number of words of each other.

Primary Source Content includes:

• Current IRS Code
• Federal Tax Regulations
• Federal Tax Cases
• IRS Administrative rulings, Letter Rulings and Memorandum
• Index

Secondary Resources include editorial matters prepared by CCH Wolters Kluwer which help explain the primary source content. 

• The U.S. Master Tax Guide may be a helpful resource to consult when researching a new area of taxation.

• The Standard Federal Income Tax Reporter, which is arranged by IRS Code, offers CCH Wolters Kluwer's experts explanations and interpretations.

Once a search is run on selected resources, the related resources are accessible through hyperlinks so one need not do separate additional searches to locate these references.

A brief tutorial of 2 minutes covers the basics.  More short training videos are available.