(CNN) -- It's been more than three weeks since militants from the dreaded Boko Haram terrorist group dragged 276 girls out of their beds at a boarding school in northern Nigeria, and still no one knows where the girls are. International assistance has begun to flow into Nigeria, whose president has vowed to end the terror threat plaguing his country. 

Here's what you need to know to get caught up: 

Where are the girls? 

It's anyone's guess. Boko Haram's leader, Abubakar Shekau, said in a video that he was going to sell them into slavery, but it's unknown whether he has. Pentagon spokesman U.S. Navy Rear Adm. John Kirby and other officials have said they believe the girls may have been separated into smaller groups, making the task of finding them inordinately more difficult. Gordon Brown, a former UK prime minister and the U.N.'s special envoy for global education, speculated that the girls may have been moved into neighboring countries. "The search must be in Niger, Cameroon and Chad, to see if we can find information," he said. 

What's being done to find them? 

Nigeria hasn't given a lot of information about its efforts other than to say that its soldiers have been out in the field, looking for the girls. Nigerian police offered a $310,000 reward, but there's no evidence that has turned up any leads. The United States and Britain have sent advisers to help the Nigerian government find the girls, stage rescue missions and help in the larger fight to defeat Boko Haram. 
How many girls?
Who took them?
Where were they before they were taken?
Who is helping?
Who is in charge of hostages?
Where are they searching?
What did he claim he would do to the hostages?
Has he done this?
Has there been any clues to there whereabouts?
Is there an incentive to locate them?
What is it?
Who needs to be defeated?
Why is it difficult to find them?
Who is speaking about this?
Is there another person?
Who is advising?
Who is fighting terror?
Who put out a video?
What role does he have?
How long have they been missing?
What is Boko haram?
Where they taken in the daytime?
Where are they thought to be now?
276
 It's been more than three weeks since militants from the dreaded Boko Haram terrorist group dragged 276 girls out of their beds at a boarding school in northern Nigeria,
Boko Haram
It's been more than three weeks since militants from the dreaded Boko Haram terrorist group dragged 276 girls out of their beds at a boarding school in northern Nigeria,
a boarding school in northern Nigeria
 Boko Haram terrorist group dragged 276 girls out of their beds at a boarding school in northern Nigeria, 
the United States and Britain
The United States and Britain have sent advisers to help the Nigerian government find the girls, 
unknown
unknown
Niger, Cameroon and Chad
 "The search must be in Niger, Cameroon and Chad, to see if we can find information," he said. 
sell them into slavery
Boko Haram's leader, Abubakar Shekau, said in a video that he was going to sell them into slavery,
it's unknown
Boko Haram's leader, Abubakar Shekau, said in a video that he was going to sell them into slavery, but it's unknown whether he has. 
no
Nigeria hasn't given a lot of information about its efforts other than to say that its soldiers have been out in the field, looking for the girls. Nigerian police offered a $310,000 reward, but there's no evidence that has turned up any leads.
yes
Nigerian police offered a $310,000 reward, 
a $310,000 reward
Nigerian police offered a $310,000 reward,
Boko Haram
 The United States and Britain have sent advisers to help the Nigerian government find the girls, stage rescue missions and help in the larger fight to defeat Boko Haram.
the girls may have been seaprated
 John Kirby and other officials have said they believe the girls may have been separated into smaller groups, making the task of finding them inordinately more difficult. 
Pentagon spokesman U.S. Navy Rear Adm. John Kirby
Pentagon spokesman U.S. Navy Rear Adm. John Kirby and other officials have said they believe the girls may have been separated
other officials
Pentagon spokesman U.S. Navy Rear Adm. John Kirby and other officials have said they believe the girls may have been separated into smaller groups,
The United States and Britain have sent advisers
 The United States and Britain have sent advisers to help the Nigerian government 
the Nigerian government
to help the Nigerian government find the girls, stage rescue missions and help in the larger fight to defeat Boko Haram
Abubakar Shekau
It's anyone's guess. Boko Haram's leader, Abubakar Shekau, said in a video that he was going to sell them into slavery,
he's Boko Haram's leader
Boko Haram's leader, Abubakar Shekau
3 weeks
t's been more than three weeks since militants from the dreaded Boko Haram terrorist group dragged 276 girls out of their beds at a boarding school in northern Nigeria, 
a terrorist group
from the dreaded Boko Haram terrorist group 
no
 It's been more than three weeks since militants from the dreaded Boko Haram terrorist group dragged 276 girls out of their beds
It's anyone's guess
Where are the girls? 

It's anyone's guess.