diff --git a/README.md b/README.md
index c6ef532..d132d39 100644
--- a/README.md
+++ b/README.md
@@ -148,7 +148,7 @@ This course will introduce you to the world of computer science. Students who ha
 
 Courses | Duration | Effort | Prerequisites
 :-- | :--: | :--: | :--:
-[Introduction to Computer Science and Programming using Python](https://www.edx.org/course/introduction-computer-science-mitx-6-00-1x-10) ([alt](https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-0001-introduction-to-computer-science-and-programming-in-python-fall-2016/)) | 9 weeks | 15 hours/week | high school algebra
+[Introduction to Computer Science and Programming using Python](https://www.edx.org/course/introduction-computer-science-mitx-6-00-1x-10) ([alt](https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-0001-introduction-to-computer-science-and-programming-in-python-fall-2016/)) | 9 weeks | 15 hours/week | [high school algebra](https://www.khanacademy.org/math/algebra-home)
 
 ## Core CS
 
@@ -191,25 +191,25 @@ Courses | Duration | Effort | Prerequisites
 #### Calculus
 Courses | Duration | Effort | Prerequisites
 :-- | :--: | :--: | :--:
-[Calculus 1A: Differentiation](https://www.edx.org/course/calculus-1a-differentiation) | 13 weeks | 6-10 hours/week | pre-calculus
+[Calculus 1A: Differentiation](https://www.edx.org/course/calculus-1a-differentiation) | 13 weeks | 6-10 hours/week | [pre-calculus](https://www.futurelearn.com/courses/precalculus)
 [Calculus 1B: Integration](https://www.edx.org/course/calculus-1b-integration) | 13 weeks | 5-10 hours/week | Calculus 1A
 [Calculus 1C: Coordinate Systems & Infinite Series](https://www.edx.org/course/calculus-1c-coordinate-systems-infinite-series) | 13 weeks | 5-10 hours/week | Calculus 1B
 
 #### Linear Algebra
 Courses | Duration | Effort | Prerequisites
 :-- | :--: | :--: | :--:
-[Essence of Linear Algebra](https://www.youtube.com/playlist?list=PLZHQObOWTQDPD3MizzM2xVFitgF8hE_ab) | - | - | pre-calculus
+[Essence of Linear Algebra](https://www.youtube.com/playlist?list=PLZHQObOWTQDPD3MizzM2xVFitgF8hE_ab) | - | - | [pre-calculus](https://www.futurelearn.com/courses/precalculus)
 [Linear Algebra - Foundations to Frontiers](https://www.edx.org/course/linear-algebra-foundations-to-frontiers-0) ([alt](http://ulaff.net/)) | 15 weeks | 8 hours/week | Essence of Linear Algebra
 
 #### Logic
 Courses | Duration | Effort | Prerequisites
 :-- | :--: | :--: | :--:
-[Introduction to Logic](https://www.coursera.org/learn/logic-introduction) | 10 weeks | 4-8 hours/week | set theory
+[Introduction to Logic](https://www.coursera.org/learn/logic-introduction) | 10 weeks | 4-8 hours/week | [set theory](https://www.youtube.com/playlist?list=PL5KkMZvBpo5AH_5GpxMiryJT6Dkj32H6N)
 
 #### Probability
 Courses | Duration | Effort | Prerequisites
 :-- | :--: | :--: | :--:
-[Introduction to Probability - The Science of Uncertainty](https://www.edx.org/course/introduction-probability-science-mitx-6-041x-2) | 18 weeks | 12 hours/week | Multivariable Calculus
+[Introduction to Probability - The Science of Uncertainty](https://www.edx.org/course/introduction-probability-science-mitx-6-041x-2) | 18 weeks | 12 hours/week | [Multivariable Calculus](https://ocw.mit.edu/courses/mathematics/18-02sc-multivariable-calculus-fall-2010/index.htm)
 
 ### Core Math
 In addition to their math elective, students must complete the following course on discrete mathematics.
@@ -375,7 +375,7 @@ Courses | Duration | Effort | Prerequisites
 
 Courses | Duration | Effort | Prerequisites
 :-- | :--: | :--: | :--:
-[Electricity and Magnetism, Part 1](https://www.edx.org/course/electricity-magnetism-part-1-ricex-phys102-1x-0)<sup>1</sup> | 7 weeks | 8-10 hours/week | calculus, basic mechanics
+[Electricity and Magnetism, Part 1](https://www.edx.org/course/electricity-magnetism-part-1-ricex-phys102-1x-0)<sup>1</sup> | 7 weeks | 8-10 hours/week | [calculus](https://www.khanacademy.org/math/calculus-1), [basic mechanics](https://www.khanacademy.org/science/physics)
 [Electricity and Magnetism, Part 2](https://www.edx.org/course/electricity-magnetism-part-2-ricex-phys102-2x-0) | 7 weeks | 8-10 hours/week | Electricity and Magnetism, Part 1
 [Computation Structures 1: Digital Circuits](https://www.edx.org/course/computation-structures-part-1-digital-mitx-6-004-1x-0) | 10 weeks | 6 hours/week | electricity, magnetism
 [Computation Structures 2: Computer Architecture](https://www.edx.org/course/computation-structures-2-computer-mitx-6-004-2x) | 10 weeks | 6 hours/week | Computation Structures 1
@@ -422,7 +422,7 @@ So if you don't wish to spend money or use the Capstone as your Final, it may be
 
 Courses | Duration | Effort | Prerequisites
 :-- | :--: | :--: | :--:
-[Modern Robotics (Specialization)](https://www.coursera.org/specializations/modernrobotics) | 26 weeks | 2-5 hours/week | freshman-level physics, linear algebra, calculus, linear ordinary differential equations
+[Modern Robotics (Specialization)](https://www.coursera.org/specializations/modernrobotics) | 26 weeks | 2-5 hours/week | freshman-level physics, linear algebra, calculus, [linear ordinary differential equations](https://www.khanacademy.org/math/differential-equations)
 [Data Mining (Specialization)](https://www.coursera.org/specializations/data-mining) | 30 weeks | 2-5 hours/week | machine learning
 [Big Data (Specialization)](https://www.coursera.org/specializations/big-data) | 30 weeks | 3-5 hours/week | none
 [Internet of Things (Specialization)](https://www.coursera.org/specializations/internet-of-things) | 30 weeks | 1-5 hours/week | strong programming