Stevenson, Noel C. Genealogical Evidence: A Guide to the Standard of Proof Relating to Pedigrees, Ancestry, Heirship and Family History. Laguna Hills, California: Aegean Park Press, 1979, revised 1989.
What can you learn from a book written almost 35 years ago and revised 25 years ago? A lot!
To state the case most simply: if you are working on your portfolio, you need to have this book close by. Let me explain why.
Noel C. Stevenson, J.D., FASG is one of genealogy’s icons of the most recent past generation, serving as President of the American Society of Genealogists from 1985-1986.  His book, Genealogical Evidence is recognized as a pioneer in defining a common genealogical vocabulary, constructing a standard for source analysis and providing guidance for assessment of evidence. Thus, in the genealogy of genealogy, this book is an “ancestor” to Evidence Explained by Elisabeth Shown Mills and Mastering Genealogical Proof by Tom Jones. 
The content covers common genealogical problems and establishes guidelines for their assessment. For example, The first chapter on “Paternity, Maternity, Legitimacy and Illegitimacy” discusses “Age and Paternity” and “Age and Maternity,” where Stevenson discusses the ages one can expect parents to be within and ones that are outside that realm. When you are looking at the age of the father at 16 and the age of the mother at 13 in your case study, what do you say about the likelihood of that happening? Stevenson will give you guidance and his work is a respected source. Is your case study a question of identity? If so, Stevenson has an entire chapter on that topic.
Stevenson then breaks down records into two groups — public and unofficial records, the latter being everything that isn’t public, such as bibles, church records, tombstones etc., and covers types of records within those two broad categories. With each source type he begins with a short history of the development, and then describes their relative accuracy. Another great inclusion is the list at the end of these chapters which describe the various locations one can obtain the information desired if the single source does not exist. The list for location of evidence of marriage, considered a public record, is 21 items long. These other locations for marriage records may assist you in breaking down some of your brick walls or verify that you have truly completed your “exhaustive research.”
As a lawyer, his narrative concerning court records is especially note worthy. Stevenson brings a depth of understanding of the types of courts, their history and the records found there. He covers the types of marriages and the legality by state of common law marriages. In this era, laws of marriage are changing so rapidly this list may be outdated, but it gives you a place to start. This section (and others) are laced with examples which focus the reader on the analysis and the conclusions that can be drawn from the court records. He even discusses, with examples, false pedigrees and some of the genealogical hoaxes that have been committed and still exist today.
Val Greenwood’s book, The Researcher’s Guide to American Genealogy, another iconic book, looks at source types; Stevenson’s addresses source types but then investigates each source type for the type of information it might contain and discusses the inherent validity of the evidence you may find within that source type. It is true that Stevenson uses terms like “circumstantial evidence” which now are dated, but this does not obviate the quality of the contents within.
If you are “on the clock,” this book will provide you with a basis for assumptions, will give you a basis for analyzing your sources and give you hints as to other locations to find records which make for a more complete research effort. In addition, his citations may lead you to other documents, articles and books to assist you in solving a particular problem. However, this is not a “brick wall problem solvers guide” as it is not focused on a particular problem you might have but rather the book provides us with a road map for our every day genealogical assessment.
What I have done since the last posting: I made my research plan for the holiday weekend. I also listened to Ron Arons Legacy Webinar on mapping. He did a nice job and Geoff Rasmussen, the host, gave my webinar presentation on fire insurance maps (scheduled for April) a shout out to all the live listeners.
 American Society of Genealogists, “Past Officers” (http://fasg.org/fellows/past-officers/ : accessed 25 November 2015).
 John (surname not given), “Elements of Genealogical Analysis,” Our Blog (Allen County (IN) Public Library Genealogy Center), blog, 13 November 2014 (http://www.genealogycenter.org/Community/Blog/acpl-genealogy-blog/2014/11/13/elements-of-genealogical-analysis : accessed 25 November 2015).
 Do I really need to provide a citation for you?