I have following directory structure:
D:\\PROJECT
+---javaGradleProject1
+---javaGradleProject2
+---javaGradleProject3
\\---AndroidProject
|
I was able to solve this by deleting the settings.gradle file from every Gradle project that I wanted to use as dependency (clearing the contents of this file was not enough).
NOTE: As I have little knowledge of Gradle and Android Studio, I cannot provide information about why the presence of this file does not allow Android Studio to include the Gradle project as a module.