[tag=DT] [lemma=begin] [lemma=because] [lemma=□]
[tag=DT] [lemma=begin] [lemma=because] [lemma=the]
[tag=DT] [lemma=begin] [lemma=because] [lemma=begin]
When building a map , it is difficult and slow at the beginning because the first markers cannot be associated with one another .