Abstract: In bilevel optimization, the upper-level optimization problem (ULOP) requires to be solved under the constraint of the inner lower-level optimization problem (LLOP). However, it is ...

Six days into Savannah Guthrie’s mom Nancy’s disappearance, a break down of the “very detailed” ransom note reveals a crucial clue. TMZ founder Harvey Levin appeared on CNN Thursday after the first ...

The FBI has confirmed the existence of a ransom letter for Nancy Guthrie, the mother of "Today" show host Savannah Guthrie. STEVE INSKEEP, HOST: This was the letter that a few media outlets received ...

Nancy Guthrie disappearance: FBI, White House assist search, analyze ransom note Attorney General Pam Bondi and the FBI confirm federal aid in the search for Nancy Guthrie, who went missing in Tucson, ...

The FBI said that the ransom note they are investigating in relation to the disappearance of Nancy Guthrie, the mother of "TODAY" co-host Savannah Guthrie, gave a deadline of 5 p.m. on February 5.

As the search for Savannah Guthrie’s missing mother continues, authorities say they are investigating a new message regarding her disappearance and are urging anyone with tips to contact the FBI. NBC ...

• Son’s plea: Nancy Guthrie’s son issued a new appeal to possible captors to reach out, saying in a video “we want to hear from you,” as the first deadline in an apparent ransom note passed. A second ...

Two news outlets have received an alleged ransom note and law enforcement said it is investigating whether it is connected to the disappearance of Nancy Guthrie, 84-year-old mother of Today co-anchor ...

CNN reported that two notes were sent, but it has not been confirmed if they are legitimate. Pima County Sheriff Chris Nanos said they are “absolutely not” dismissing the notes. “When the note comes ...

In a wrenching video posted to Instagram on Wednesday evening, “Today” anchor Savannah Guthrie pleaded for her missing mother to come home days after her apparent abduction from her Tuscon-area home. ...