The Princeton Environmental Association have worked for decades with one clearly defined goal: to reduce the negative impact of human activity
on the natural world.
change have to has

the present continuous is a verb tense which is mainly used to indicates that an action is in progress at the moment of speaking.  

it is formed using: person + verb to be (am/is/are) +verb + - ing form  

example: i am studying at this moment .

in addition, the present continuous is also used in order to express things that will or will not happen in the near future.

example: i am having dinner with some friends tonight.

the speaker sometimes   uses it   to express that an action is repeated and it causes irritation on the part of the speaker

example: my sister is constantly complaining about everything.

i've read it so how can i ?

in "people in peace, not profit and war" chrisholm uses inductive reasoning for her argument against defense spending by stating that the new administration, like most americans, wanted to invest in social objectives, so they must not want to prioritize defense spending. mr. nixon said "we can delay no longer in launching new approaches to the problem that beset them", but chrisholm points out that the programs were delayed anyways.