Hi. I thought this question had been exhausted a long time ago, and everyone is googling for pictures. But I realize that google does not always give the necessary pictures. Since this is a research paper, I understand you need different kinds of hills, including rolling hills. You can use various scientific sites to find such images, or you can use vector image sites, which also provide a huge selection of different images.
Doesn't google have enough pictures on this subject? You could also try Pinterest or Tumblr for pictures of hills.....
Hi. I thought this question had been exhausted a long time ago, and everyone is googling for pictures. But I realize that google does not always give the necessary pictures. Since this is a research paper, I understand you need different kinds of hills, including rolling hills. You can use various scientific sites to find such images, or you can use vector image sites, which also provide a huge selection of different images.