References often cite original sources such as medical journals. 
Dr. Williams (Alternatives newsletter (Alt.)) is particularly conscientious, which is one of the reasons I subscribe.

Abbreviations used for references

 Alt  Alternatives (by Dr. David G. Williams,
 BN  Better Nutrition (local freebie by Primedia)
 DL  Delicious Living (local freebie,
 HFN  Health Freedom News (National Health Federation)
 HNB  Health and Nutrition Breakthroughs (local freebie,
 HS  Health Science (National Health Association
 NAH  Nutrition Action Healthletter (CSPI,
 SN  Science News
SNol  Science News online where ???????? is the eight digit number in the reference.  These articles often contain many references.
 WBJ  Well Being Journal (
 WSH  Dr. Andrew Weil's Self Healing (