  Electronic Theses and Dissertations (ETDs) contain domain knowledge that can
be used for many digital library tasks, such as analyzing citation networks and
predicting research trends. Automatic metadata extraction is important to build
scalable digital library search engines. Most existing methods are designed for
born-digital documents, so they often fail to extract metadata from scanned
documents such as for ETDs. Traditional sequence tagging methods mainly rely on
text-based features. In this paper, we propose a conditional random field (CRF)
model that combines text-based and visual features. To verify the robustness of
our model, we extended an existing corpus and created a new ground truth corpus
consisting of 500 ETD cover pages with human validated metadata. Our
experiments show that CRF with visual features outperformed both a heuristic
and a CRF model with only text-based features. The proposed model achieved
81.3%-96% F1 measure on seven metadata fields. The data and source code are
publicly available on Google Drive (https://tinyurl.com/y8kxzwrp) and a GitHub
repository (https://github.com/lamps-lab/ETDMiner/tree/master/etd_crf),
respectively.
