CONSENT OF ARTHUR ANDERSEN LLP
Published on March 26, 2002
EXHIBIT 23.1
Consent of Independent Public Accountants
As independent public accountants, we hereby consent to the incorporation of our
report included in this Form 10-K, into the Company's previously filed
Registration Statements on Form S-8 No. 333-16837, on Form S-8 No. 333-56089, on
Form S-3 No. 333-87063, on Form S-3 No. 333-15407, on Form S-3 No. 333-62855, on
Form S-3 No. 333-57888 and on Form S-3 No. 333-87219.
/s/ Arthur Andersen LLP
Vienna, Virginia
March 25, 2002