My IELTS score was 7.0 (reading 8, Writing 7, Speaking 6.5, listening 7) about 4 years ago. Since then I have studied for my PhD abroad and I thought my English has been considerably improved (English is being used as the educational language in our university).
However, according below test my vocabulary is around 7000 words (equal to a 5-6 years old native kid!).
I want to increase that to something above 10,000-11,000.
Could someone please suggest me a reference or a reading collection (designed/selected for vocabulary improvement)? Or if there is no such a thing perhaps you can advise on how to achieve my learning target.