You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: A Review of Facial Landmark Extraction in 2D Images and Videos Using Deep Learning 
Chapter Title:  • 
1. Abstract of Cited Paper (BIB001):  We present a novel approach to localizing parts in images of human faces. The approach combines the output of local detectors with a non-parametric set of global models for the part locations based on over one thousand hand-labeled exemplar images. By assuming that the global models generate the part locations as hidden variables, we derive a Bayesian objective function. This function is optimized using a consensus of models for these hidden variables. The resulting localizer handles a much wider range of expression, pose, lighting and occlusion than prior ones. We show excellent performance on a new dataset gathered from the internet and show that our localizer achieves state-of-the-art performance on the less challenging BioID dataset. 
2. Abstract of Cited Paper (BIB002):  We address the problem of interactive facial feature localization from a single image. Our goal is to obtain an accurate segmentation of facial features on high-resolution images under a variety of pose, expression, and lighting conditions. Although there has been significant work in facial feature localization, we are addressing a new application area, namely to facilitate intelligent high-quality editing of portraits, that brings requirements not met by existing methods. We propose an improvement to the Active Shape Model that allows for greater independence among the facial components and improves on the appearance fitting step by introducing a Viterbi optimization process that operates along the facial contours. Despite the improvements, we do not expect perfect results in all cases. We therefore introduce an interaction model whereby a user can efficiently guide the algorithm towards a precise solution. We introduce the Helen Facial Feature Dataset consisting of annotated portrait images gathered from Flickr that are more diverse and challenging than currently existing datasets. We present experiments that compare our automatic method to published results, and also a quantitative evaluation of the effectiveness of our interactive method. 
3. Abstract of Cited Paper (BIB003):  We present a unified model for face detection, pose estimation, and landmark estimation in real-world, cluttered images. Our model is based on a mixtures of trees with a shared pool of parts; we model every facial landmark as a part and use global mixtures to capture topological changes due to viewpoint. We show that tree-structured models are surprisingly effective at capturing global elastic deformation, while being easy to optimize unlike dense graph structures. We present extensive results on standard face benchmarks, as well as a new “in the wild” annotated dataset, that suggests our system advances the state-of-the-art, sometimes considerably, for all three tasks. Though our model is modestly trained with hundreds of faces, it compares favorably to commercial systems trained with billions of examples (such as Google Picasa and face.com). 
4. Abstract of Cited Paper (BIB004):  Abstract This paper presents a comprehensive survey of facial feature point detection with the assistance of abundant manually labeled images. Facial feature point detection favors many applications such as face recognition, animation, tracking, hallucination, expression analysis and 3D face modeling. Existing methods are categorized into two primary categories according to whether there is the need of a parametric shape model: parametric shape model-based methods and nonparametric shape model-based methods. Parametric shape model-based methods are further divided into two secondary classes according to their appearance models: local part model-based methods (e.g. constrained local model) and holistic model-based methods (e.g. active appearance model). Nonparametric shape model-based methods are divided into several groups according to their model construction process: exemplar-based methods, graphical model-based methods, cascaded regression-based methods, and deep learning based methods. Though significant progress has been made, facial feature point detection is still limited in its success by wild and real-world conditions: large variations across poses, expressions, illuminations, and occlusions. A comparative illustration and analysis of representative methods provides us a holistic understanding and deep insight into facial feature point detection, which also motivates us to further explore more promising future schemes. 
5. Abstract of Cited Paper (BIB005):  Detection and tracking of faces in image sequences is among the most well studied problems in the intersection of statistical machine learning and computer vision. Often, tracking and detection methodologies use a rigid representation to describe the facial region 1, hence they can neither capture nor exploit the non-rigid facial deformations, which are crucial for countless of applications (e.g., facial expression analysis, facial motion capture, high-performance face recognition etc.). Usually, the non-rigid deformations are captured by locating and tracking the position of a set of fiducial facial landmarks (e.g., eyes, nose, mouth etc.). Recently, we witnessed a burst of research in automatic facial landmark localisation in static imagery. This is partly attributed to the availability of large amount of annotated data, many of which have been provided by the first facial landmark localisation challenge (also known as 300-W challenge). Even though now well established benchmarks exist for facial landmark localisation in static imagery, to the best of our knowledge, there is no established benchmark for assessing the performance of facial landmark tracking methodologies, containing an adequate number of annotated face videos. In conjunction with ICCV'2015 we run the first competition/challenge on facial landmark tracking in long-term videos. In this paper, we present the first benchmark for long-term facial landmark tracking, containing currently over 110 annotated videos, and we summarise the results of the competition. 
6. Abstract of Cited Paper (BIB006):  Computer Vision has recently witnessed great research advance towards automatic facial points detection. Numerous methodologies have been proposed during the last few years that achieve accurate and efficient performance. However, fair comparison between these methodologies is infeasible mainly due to two issues. (a) Most existing databases, captured under both constrained and unconstrained (in-the-wild) conditions have been annotated using different mark-ups and, in most cases, the accuracy of the annotations is low. (b) Most published works report experimental results using different training/testing sets, different error metrics and, of course, landmark points with semantically different locations. In this paper, we aim to overcome the aforementioned problems by (a) proposing a semi-automatic annotation technique that was employed to re-annotate most existing facial databases under a unified protocol, and (b) presenting the 300 Faces In-The-Wild Challenge (300-W), the first facial landmark localization challenge that was organized twice, in 2013 and 2015. To the best of our knowledge, this is the first effort towards a unified annotation scheme of massive databases and a fair experimental comparison of existing facial landmark localization systems. The images and annotations of the new testing database that was used in the 300-W challenge are available from http://ibug.doc.ic.ac.uk/resources/300-W_IMAVIS/. 
7. Abstract of Cited Paper (BIB007):  Over the last two decades, face alignment or localizing fiducial facial points has received increasing attention owing to its comprehensive applications in automatic face analysis. However, such a task has proven extremely challenging in unconstrained environments due to many confounding factors, such as pose, occlusions, expression and illumination. While numerous techniques have been developed to address these challenges, this problem is still far away from being solved. In this survey, we present an up-to-date critical review of the existing literatures on face alignment, focusing on those methods addressing overall difficulties and challenges of this topic under uncontrolled conditions. Specifically, we categorize existing face alignment techniques, present detailed descriptions of the prominent algorithms within each category, and discuss their advantages and disadvantages. Furthermore, we organize special discussions on the practical aspects of face alignment in-the-wild, towards the development of a robust face alignment system. In addition, we show performance statistics of the state of the art, and conclude this paper with several promising directions for future research. 
8. Abstract of Cited Paper (BIB008):  In this paper, we present a new benchmark (Menpo benchmark) for facial landmark localisation and summarise the results of the recent competition, so-called Menpo Challenge, run in conjunction to CVPR 2017. The Menpo benchmark, contrary to the previous benchmarks such as 300-W and 300-VW, contains facial images both in (nearly) frontal, as well as in profile pose (annotated with a different markup of facial landmarks). Furthermore, we increase considerably the number of annotated images so that deep learning algorithms can be robustly applied to the problem. The results of the Menpo challenge demonstrate that recent deep learning architectures when trained with the abundance of data lead to excellent results. Finally, we discuss directions for future benchmarks in the topic. 
9. Abstract of Cited Paper (BIB009):  Recently, deformable face alignment is synonymous to the task of locating a set of 2D sparse landmarks in intensity images. Currently, discriminatively trained Deep Convolutional Neural Networks (DCNNs) are the state-of-the-art in the task of face alignment. DCNNs exploit large amount of high quality annotations that emerged the last few years. Nevertheless, the provided 2D annotations rarely capture the 3D structure of the face (this is especially evident in the facial boundary). That is, the annotations neither provide an estimate of the depth nor correspond to the 2D projections of the 3D facial structure. This paper summarises our efforts to develop (a) a very large database suitable to be used to train 3D face alignment algorithms in images captured "in-the-wild" and (b) to train and evaluate new methods for 3D face landmark tracking. Finally, we report the results of the first challenge in 3D face tracking "in-the-wild".

Literature Review:
The 300-W BIB007 dataset (300 Faces in-the-Wild Challenge). Among all in-the-wild datasets, this has been the most popular one in recent years and it combines several datasets, such as Helen BIB003 , LFPW BIB002 , AFW BIB004 , and a newly introduced challenging dataset, iBug. Summing up, it contains 3837 images and a further test set with 300 indoor and outdoor images, respectively. All the images are annotated with 68 points. The dataset is commonly divided in two parts: the usual subset, including LFPW and Helen, and the challenging dataset with AFW and iBug. The Menpo BIB009 dataset. It is the largest in-the-wild facial landmark dataset, and contains 6679 semi-front view face images, annotated with 68 points, and 5335 profile view face images, annotated with 39 points in the training set. The test set is composed of 12006 front view images and 4253 profile view images. It was introduced for the Menpo challenge in 2017 in order to raise an even more difficult challenge to test the robustness of facial landmark extraction algorithms, since it involves a high variation of poses, light conditions, and occlusions. Video-based annotated datasets are used for sequential facial landmark extraction. The 300-VW BIB006 has the largest number of facial-point annotated videos and frames. The dataset is composed by 50 training videos and 64 videos for testing, which are further divided into three scenarios, according to different light conditions, expressions, head poses, and occlusions. All of the frames are annotated in 68 points in a semi-automatic manner. The Menpo 3D tracking BIB010 dataset is the unique dataset in which 3D facial landmarks are annotated in video by the 3DMM algorithm  . The dataset contains 55 videos from the 300VW dataset, annotated again in 3D, in addition to all of the images in 300W, and Menpo re-annotated in the same way. The dataset provides us not only the landmarks in projected image space, but also the landmarks in 3D space. The number of landmarks and their accuracy requirements: The accuracy requirements and the number of landmark points vary based on the intended application. For example, coarser detection of only the primary landmarks, e.g., nose tip, four eye and two mouth corners, or even the bounding box enclosing these landmarks, may be adequate for face detection or face recognition tasks. On the other hand, higher-level tasks, such as facial expression understanding or facial animation, require a greater number for landmarks that is from 20-30 to 60-80, as well as greater spatial accuracy. As for the accuracy requirement, fiducial landmarks, such as on the eyes and nose, need to be determined more accurately as they often guide the search for secondary landmarks with less prominent or reliable image evidence. It has been observed, however, that landmarks on the rim of the face, such as the chin, cannot be accurately localized in either manual annotation and automatic detection. Shape guide algorithms can benefit from the richer information coming from a larger set of landmarks. For example, Milborrow and Nicolls BIB001 have shown that the accuracy of landmark localization increases proportionally to the number of landmarks considered, and have recorded a 50% improvement as the ensemble increases from 3 to 68 landmarks. In the final analysis, accurate and precise landmarking remains a difficult problem since, except for a few, landmarks do not necessarily correspond to high-gradient or other salient points. Hence, low-level image processing tools remain inadequate to detect them, and recourse has to be made for higher-order face shape information. This probably explains the tens of algorithms presented and the hundreds of articles published in the last two decades in the quest to develop a landmarking scheme on par with human annotators  BIB005 BIB008 .