There was a program called jami altafaseer is made by
مؤسسة نشر احاديث اهل البيت عليهم السلام في ايران.
In this quran search engine we can search for two root or more at the same time (Simultaneously) and the most important thing is that you can specify a distance in words between the roots from one 1 word to 99. through such capability of searching we can determine the relationships between words in the quran.
Unfortunately this institute has stopped updating this program. The CRCIS has made a new jami al tafasir programm called Noor jami al tafaseer . It is very nice programm but the most important feature about searching two roots at the same time with specific word distance disppeared.It can search for two roots simultaneously but It will find the roots only if they are in the same verse or( aieh ). This capability of searching multiple root seperated by predefined distance is extremely important for researchers.