Columbia subject headings:
Assassination--United States--Prevention--Congresses.
Criminal behavior, Prediction of--Congresses.
Secret service--United States--Congresses.
Harvard subject headings:
Assassination--United States--Prevention--Congresses.
Criminal behavior, Prediction of--Congresses.
Secret service--United States--Congresses.
Princeton subject headings:
Assassination--United States--Prevention--Congresses.
Criminal behavior, Prediction of--Congresses.
Secret service--United States--Congresses.