Instruction: First, identify the target attributes from the provided list. Then, scan the product title, description, feature, and brand to extract the values associated with each target attribute. Finally, create a list of dictionaries, each containing the extracted attribute, its corresponding value, and the source where it was found.

Input:
Product title: D'Addario J30 Acoustic Guitar Strings
Product description: SET CLASSICS RECT/SILVER NORM
Product feature: Silver wound on nylon basses with clear rectified nylon trebles, Rectified nylon trebles for unsurpassed intonation, Environmentally friendly, corrosion resistant packaging for strings that are always fresh, Made in the U.S.A. for the highest quality and performance, Silver wound on nylon basses with clear rectified nylon trebles
Product brand: D'Addario
Target attributes: Gauge
Answer: attribute: gauge
value: None
source: None