  Context: A Multivocal Literature Review (MLR) is a form of a Systematic
Literature Review (SLR) which includes the grey literature (e.g., blog posts
and white papers) in addition to the published (formal) literature (e.g.,
journal and conference papers). MLRs are useful for both researchers and
practitioners since they provide summaries both the state-of-the art and
-practice in a given area. Objective: There are several guidelines to conduct
SLR studies in SE. However, given the facts that several phases of MLRs differ
from those of traditional SLRs, for instance with respect to the search process
and source quality assessment. Therefore, SLR guidelines are only partially
useful for conducting MLR studies. Our goal in this paper is to present
guidelines on how to conduct MLR studies in SE. Method: To develop the MLR
guidelines, we benefit from three inputs: (1) existing SLR guidelines in SE,
(2), a literature survey of MLR guidelines and experience papers in other
fields, and (3) our own experiences in conducting several MLRs in SE. All
derived guidelines are discussed in the context of three examples MLRs as
running examples (two from SE and one MLR from the medical sciences). Results:
The resulting guidelines cover all phases of conducting and reporting MLRs in
SE from the planning phase, over conducting the review to the final reporting
of the review. In particular, we believe that incorporating and adopting a vast
set of recommendations from MLR guidelines and experience papers in other
fields have enabled us to propose a set of guidelines with solid foundations.
Conclusion: Having been developed on the basis of three types of solid
experience and evidence, the provided MLR guidelines support researchers to
effectively and efficiently conduct new MLRs in any area of SE.
