diff --git a/content/roadmaps/104-angular/content/101-rxjs-basics/102-marble-diagrams.md b/content/roadmaps/104-angular/content/101-rxjs-basics/102-marble-diagrams.md
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--- a/content/roadmaps/104-angular/content/101-rxjs-basics/102-marble-diagrams.md
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-# Marble diagrams
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+# Marble Diagrams
+
+Marble testing allows you to test asynchronous RxJS code synchronously and step-by-step with the help of RxJS TestScheduler test utility and using virtual time steps.
+
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.altamira.ai/blog/angular-marble-testing-a-brief-introduction/'>Angular Marble Testing: A Brief Introduction</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://medium.com/@jshvarts/read-marble-diagrams-like-a-pro-3d72934d3ef5'>IUnderstanding Marble Diagrams for Reactive Streams</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://rxmarbles.com/#from'>Interactive Diagrams</BadgeLink>