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 Survey on Multimodal Biometrics and the Protection of Their Templates 
Chapter Title:  Ideas for Incorporation 
1. Abstract of Cited Paper (BIB001):  Biometric template protection techniques are able to provide a solution for vulnerability which compromises biometric template. These are expected to be useful for remote biometric authentication. However, there were no supported standard evaluation method, thus making these technology not fully trusted. The draft Recommendation ITU-T X.gep: 'A guideline for evaluating telebiometric template protection techniques' which is currently under development at ITU-T SG 17 Question 9 (telebiometrics) aims to fill this need. ITU-T X.gep describes a general guideline for testing and reporting the performance of biometric template protection techniques based on biometric cryptosystem and cancellable biometrics. This guideline specifies two reference models for evaluation which use biometric template protection techniques in telebiometrics system. Then, it defines the metrics, procedures, and requirements for testing and evaluating the performance of the biometric template protection techniques. In addition, this Recommendation ITU-T X.gep has been approved at April 2012, and pre-published as ITU-T X.1091. 
2. Abstract of Cited Paper (BIB002):  Multi-biometric systems are known to be universal and more accurate in biometric recognition. However, the storage of multiple biometric templates as separate entities pose major threats to user privacy and system security. Therefore, we propose to fuse multiple biometric modalities at the feature level in order to obtain an integrated template and to secure the fused templates using a hybrid template protection method. The proposed method is made out of a feature transformation technique known as Random Tiling and an equal-probable 2^N discretization scheme. The former enables the revocability of the template and the latter converts the feature elements into binary representations according to the area under the genuine interval curve, in order to offer better privacy protection to the template. Our experimental results show that the proposed multi-biometric template protection scheme demonstrates better verification results as compared to their unibiometric counterparts while preserving template security. 
3. Abstract of Cited Paper (BIB003):  Abstract In this work adaptive Bloom filter-based transforms are applied in order to mix binary iris biometric templates at feature level, where iris-codes are obtained from both eyes of a single subject. The irreversible mixing transform, which generates alignment-free templates, obscures information present in different iris-codes. In addition, the transform is parameterized in order to achieve unlinkability, implementing cancelable multi-biometrics. Experiments which are carried out on the IITD Iris Database version 1.0 confirm the soundness of the proposed approach, (1) maintaining biometric performance at equal error rates below 0.5% for different feature extraction methods and fusion scenarios and (2) achieving a compression of mixed templates down to 10% of original size.

Literature Review:
Industrial projects are focused on the creation of a generic framework, similar to the one schematically presented below. The system should be capable of incorporating n templates, without the necessity to follow specific fusion levels for their representation, (k representations could be involved). The process is continued with a common representation and then the generic system is applied for the protection of the template (Fig. 2) . Analysing the idea from the levels aspect, focusing on the first part of this representation, it seems that biometrics fusion on feature level is the most suitable approach for the protection of the templates. Of course, score level fusion is not enough, besides the approaches of a solutions that offers to many systems. Nevertheless, cancelable biometric systems based on score level fusion can be reconstructed, in an analogous way to conventional, but their use to cryptosystems applications is not really popular BIB001 . Decisions based on final decisions can be successfully implemented to both system protection areas. Following the design of this framework, some issues arise, such as the template alignments, the way of the combination for modalities, the implementation in applications for the representation of the features BIB003 , the level of the obtained recognition performance, the correction of the errors and the overall security of the system, and the way the latter comes to solve any privacy related themes BIB002 . More precisely, a construction of an align-invariant biometric cryptosystem or cancelable biometrics is not yet fully investigated. Feature level fusion of templates hinders a proper alignment of protected templates, while auxiliary data for the use of alignment may leak information on stored templates. Helper data techniques can probably provide some solution, but this is still unsure. The desired code length also remains evasive, and this comes to affect the necessity for error-correction codes. The fact that false rejection rates are lower bounded by error-correction capacities emerges as a great challenge since each change can make the system more vulnerable. The representation of the feature can bring better results but it may necessitate extended efforts in the direction of combination of many different templates using the fuzzy vault schemes methodology. Finally, from a biometric template protection perspective, the length of the keys remains a major topic for discussion. In conclusion, experiments that have been carried out in different studies with use of multiple combinations of biometric samples from the same identity and implemented in several template protection technologies, illustrate significant improvements with regards to reliability of the relevant applications. Different proposals of frameworks for the design of cryptosystems or cancelable biometrics that contain many modalities, have been presented enriching this research field. In spite of the encouraging results, several other issues might occur and demand further investigation BIB004 . Current literature studies are focused on the possibility to establish a generic model, which will cover the necessity for irreversibility and unlinkability, and secure enough to be used in many applications. The next section is dedicated to the emerging issues, from biometrics recognition to the protection categories, as those were presented above.