Oracle DDL trigger , identify a "drop column"

Question

In Oracle it is possible to create DDL triggers (Data Definition Language) something like

create or replace trigger trg_ddl
   before ddl
    on database
  declare
  begin
  ...
  end; 

My , doubt , how to recognize a column deletion event from a table ?

ALTER TABLE <TABLE> DROP COLUMN <COLUMN>

Doubt about syntax, I hope to be in accordance with the rules.