Sentence examples for been difficult to prettify from inspiring English sources

been difficult to control

been difficult to implement

been difficult to design

been difficult to observe

been difficult to ascertain

been difficult to perform

been difficult to develop

been difficult to recognize

been difficult to generate

been difficult to investigate

been difficult to collect

been difficult to place

been difficult to interpret

been difficult to attain

been difficult to obtain

been difficult to establish

been difficult to predict

been difficult to draw

been difficult to assemble

been difficult to validate