http://www.qiau.ac.ir/Services/elearning/zebardast/CTR07.pdf

http://web.cecs.pdx.edu/~prasads/FirstOrderCircuits.pdf

http://people.clarkson.edu/~jsvoboda/eta/acWorkout/FOC_RCandRL.html

http://www.google.com/url?sa=t&rct=j&q=first+order+circuits&source=web&cd=6&ved=0CFIQFjAF&url=http%3A%2F%2Feelab.sjtu.edu.cn%2Fdl%2Fpps%2Fchapter%25207.pps&ei=sHNMT_XjBbT44QTWvJyLAw&usg=AFQjCNFCLhukadr3ZjUN7fVo8J52r39BEg

http://opencourses.emu.edu.tr/file.php/3/Lecture_Notes/First_Order_Circuits.pdf

http://web2.clarkson.edu/class/es250carroll/Review%20for%20the%202nd%20Midterm%20Exam.htm

http://www.enel.ucalgary.ca/People/Norm/Engg225/Exams/final_03.pdf