The place to go is to your local Library... and ask for help from a librarian. The Librarian can help
you with the names of the journals and the citation information (author, title, volumes, dates, page
numbers, etc)
The library can also get copies of the articles through ILL (Interlibrary Loan) or identify a library
that has the issues so you can get them yourself.

Barbara

Thanks, I didn't see those on the page.  But they don't add up to much.

Setting the first two aside a moment, the last three don't amount
to diddly, as is usual with advertisement "evidence" two aren't
studies, and one has to do with the product's claims:

All I could get on this one was the title:
"Glucomannan in hypertensive outpatients: pilot clinical trial"

A trial using it for high blood pressure?  
What's that got to do with evidence for weight loss?
No wonder they don't include the titles in these references.

Merely a letter published in Lancet magazine, not a study.  The letter's
contents are not listed, but was apparently not about weight loss,
as the entry is titled "Treating diabetes with glucomannan"

This is not a study either, it was an article about looking *into*
researching glucomannon as alternative treatment for diabetes,
not about weight loss at all.
The article can be found at
http://www.jacn.org/cgi/content/full/20/suppl_5/370S

Now we can look at the two that at least *were* studies about glucomannan
for weight loss.

Small and brief study consisted of only 20 people, for 8 wks, of
which only 10 took glucomannan, and 10 took placebo.

In an article on the case of the FTC vs SlimAmerica, for diet product
fraud including glucomannan, This study was mentioned.  Dr. Barrett, the
Vice President of the National Council Against Health Fraud,  comments
on that study:

 One expert on the panel referred to a 1984 study of glucomannan that
 reported weight loss of 5.5 pounds over 8 weeks without any changes in
 diet or physical activity. Walsh, D.E., et al., Effect of Glucomannan
 on Obese Patients: A Clinical Study, 8 International Journal of Obesity
 289-93 (1984). In this study, patients were instructed not to deviate
 from their previously established eating and exercise patterns. This
 study is not particularly persuasive given the small number of subjects
 in the treatment group (10) and the fact that subjects did not maintain
 appropriate food diaries. There is no way to be sure that subjects did
 not change eating patterns. In fact, one of glucomannan's purported
 mechanisms of action is as a bulking agent, and the authors note it
 "added bulk in the stomach just before each meal, [which] may decrease
 the appetite and [cause subjects] to eat less at each meal."

Another small and brief study very similar to the first one except that
participants were put on a low calorie diet as well as taking glucomannan
before meals.  25 people, 3 months.  The brief Medline summary doesn't
say what they lost, but the lack of any larger follow-up study suggests
it was as flawed as the first one.

In contrast to these, here is a reference the ads don't mention,
showing NO weight loss from glucomannon. Quoting from an article
by the aforementioned Dr Barrett, "Bulking Agents" and Weight Control"
 http://www.canoe.ca/HealthAlternativeColumns/010726.html

"In 1980, Dr. Judith Stern of the University of California conducted a
 double-blind study in which the test group received 1 gram of
 glucomannan before meals, while the control group received a placebo.
 Both groups participated in a behavior modification program and lost
 weight, but no statistically significant difference in hunger ratings
 or weight loss was found between the groups."

Meanwhile, I believe I mentioned yesterday the study where glucomannon
showed no weight loss results better than much cheaper pectin fiber,
both being used to take up room in the stomach before meals.