I have not read the article in Working Women myself, but I believe, from
comments made on Lactnet, that the "University of Wisconsin study" cited
was one done by a team led by Polly Newcomb.  The study, for those
interested, is published in the New England Journal of Medicine, Vol. 330,
no. 2, January 13, 1994, pp. 81-87.  It is titled, "Lactation and a Reduced
Risk of Premenopausal Breast Cancer."  I find very interesting and
important the closing sentences of this article:  "If women who do not
breast-feed or who breast-feed for less than 3 months were to do so for 4
to 12 months, breast cancer among parous premenopausal women could be
reduced by 11 per cent, judging from current rates.  If all women with
children lactated for 24 months or longer, however, then the incidence
might be reduced by nearly 25 per cent.  This reduction would be even
greater among women who first lactate at an early age."
I heard Polly Newcomb speak about her research twice.  She spoke very
quickly and with numerous very detailed and complicated slides, so I had
difficulty absorbing all the information.  But I believe that the subjects
included under the breastfeeding group were not exclusively breastfeeding,
and no differentiation was made between token, partial, or full
breastfeeding. Women were just asked by phone whether they had ever
breastfed or not, how long, and reason for stopping.  This was recall
information, often years later.  I often wonder how even more dramatic the
results would be if careful definitions of breastfeeding were used.  I wish
researchers from now on would use the Schema for Breastfeeding Definition
developed, I believe, by Miriam Labbok. (I received it when taking the
Georgetown U. Lactation Consultant Training Program. I believe it may be
available from  the Institute for Reproductive Health, Georgetown U.
Medical Center, 2115 Wisconsin Ave., NW, Washington, DC, 20007,
(202)687-1392.)  This schema divides breastfeeding into full, patial and
token, with several clearly and simply defined subgroups.  It seems to me
it would be easy to use and would avoid lumping together those who
breastfed only a few times with those who breastfed exclusively for 6
months.  If this were used, the differences between breastfeeding and
nonbreastfeediung groups would be very clear.

I know I've gone on much too long.  Sorry!  It's just a pet concern of
mine.  I have been stepmother for 16 years of 2 kids whose mother died of
an aggressive breast cancer, diagnosed when she was 30 and had a 2 year old
and a 4 year old.
Anne Altshuler, RN, MS, IBCLC and LLL leader in Madison, WI